THE    STORY 
OF  A   PIECE   OF   COAL 


WHAT   IT  IS     vv,         ^E    IT   COMES, 
AND   V        FHLK   IT   GOES 


BY 

EDWARD   A.   MARTIN,   F.  G.  S. 

»i 

AUTHOR  OF  AMIDST  NATURE'S  REALMS,  ETC. 


WITH   THIRTY-EIGHT  ILLUSTRATIONS 


NEW    YORK 

D.    APPLETON    AND    COMPANY 
1906 


Of 

Mf 


~r 


COPYRIGHT,  1896, 
BY  D.  APPLETON   AND   COMPANYC 


PREFACE. 


THE  knowledge  of  the  marvels  which  a  piece 
of  coal  possesses  within  itself  and  which  in  obedi- 
ence to  processes  of  man's  invention  it  is  always 
willing  to  exhibit  to  an  observant  enquirer,  is 
not  so  widespread,  perhaps,  as  it  should  be,  and 
the  aim  of  this  little  book,  this  record  of  one 
page  of  geological  history,  has  been  to  bring 
together  the  principal  facts  and  wonders  con- 
nected with  it  into  the  focus  of  a  few  pages, 
where,  side  by  side,  would  be  found  the  record 
of  its  vegetable  and  mineral  history,  its  discovery 
and  early  use,  its  bearings  on  the  great  fog- 
problem,  its  useful  illuminating  gas  and  oils,  the 
question  of  the  possible  exhaustion  of  the  world's 
supply,  and  other  important  and  interesting  bear- 
ings of  coal  or  its  products. 

In  the  whole  realm  of  natural  history,  in  the 
widest  sense  of  the  term,  there  is  nothing  which 
could  be  cited  which  has  so  benefited,  so  inter- 
ested, I  might  almost  say,  so  excited  mankind,  as 
have  the  wonderful  discoveries  of  the  various 


162335 


6  PREFACE. 

products  distilled  from  gas-tar,  itself  a  distillate 
of  coal. 

Coal  touches  the  interests  of  the  botanist,  the 
geologist,  and  the  physicist ;  the  chemist,  the 
sanitarian,  and  the  merchant. 

In  the  little  work  now  before  the  reader  I 
have  endeavoured  to  recount,  without  going  into 
unnecessary  detail,  the  wonderful  story  of  a  piece 
of  coal. 

E.  A.  M. 
THORNTON  HEATH,  February,  1896. 


NOTE. — In  order  to  adapt  the  present  edition 
of  this  book  more  closely  to  the  needs  of  Ameri- 
can readers,  a  few  passages  that  were  not  appli- 
cable to  America  have  been  replaced  by  matter 
concerning  the  coal  of  this  country.  Some  minor 
changes  in  phraseology  have  also  been  made. 
D.  APPLETON  &  COMPANY. 


CONTENTS. 


CHAPTER  PAGE 

I.  THE  ORIGIN  OF  COAL  AND   THE  PLANTS  OF 

WHICH    IT    IS   COMPOSED            ....  9 

II.  A    GENERAL    VIEW    OF    THE     COAL-BEARING 

STRATA 36 

III.  VARIOUS  FORMS  OF  COAL  AND  CARBON    .        .  64 

IV.  THE  COAL-MINE  AND  ITS  DANGERS    ...  84 
V.  EARLY  HISTORY — ITS  USE  AND  ITS  ABUSE       .  101 

VI.  How  GAS  is  MADE — ILLUMINATING  OILS  AND 

BYE-PRODUCTS in 

VII.  THE  COAL  SUPPLIES  OF  THE  WORLD        .        .  140 

VIII.  THE  COAL-TAR  COLOURS 155 

CHART  SHOWING  PRODUCTS  OF  COAL       .        .  ^5 

INDEX l66 


LIST   OF   ILLUSTRATIONS. 


FIGURE  PAGE 

1.  A  Forest  of  the  Coal  period       .        .         Frontispiece 

2.  Annularia  radiata    .......  13 

3.  Rhacopteris  in&quilatera   ......  14 

4.  Frond  of  Pecopteris 15 

5.  Pecopteris  Serlii 16 

6.  Sphenopteris  affinis 17 

7.  Calamites  Suckowii 19 

8.  Calamocladus  grandis         ......  20 

9.  Asterophyllites  foliosa 21 

10.  Sphenophyllum  cuneifolium 23 

11.  Cast  of  Lepidodendron 24 

12.  Lepidodendron  longi 'folium 25 

13.  Lepidodendron  aculeatum 25 

14.  Lepidostrobus 26 

15.  Lycopodites 27 

16.  Stigmaria  ficoides 30 

17.  Section  of  Stigmaria 32 

1 8.  Sigillarian  Trunks  in  Sandstone         ....  41 

19.  Productus . .42 

20.  Encrinite  .         . 45 

21.  Encrinital  Limestone 46 

22.  Various  encrinites 47 

23.  Cyathophyllum   . •  55 

24.  Archegosaurus  minor         ......  61 

25.  Psammodus porosus 61 

26.  Orthoceras. 62 

27.  Fene stella  retipora      . 62 

28.  Goniatites  . 63 

29.  A  viculopecten  papyraceus 63 

30.  Fragment  of  Lepidodendron 77 

31.  Engine-house  at  Head  of  a  Coal-pit .         ...  85 

32.  Gas  Jet  and  Davy  Lamp   ......  92 

33.  Part  of  a  Sigillarian  Trunk 98 

34.  Inside  a  Gas-holder 114 

35.  Filling  Retorts  by  Machinery 118 

36.  "Condensers"  . 119 

37.  <4 Washers" 120 

38.  "Purifiers" 121 


/    ^     OF  THE 

UNIVERSITY 

OF 


THE  STORY  OF  A  PIECE  OF  COAL. 


CHAPTER   I.  . 

THE    ORIGIN    OF    COAL    AND    THE    PLANTS    OF 
WHICH    IT    IS    COMPOSED. 

FROM  the  homely  scuttle  of  coal  at  the  side  of 
the  hearth  to  the  gorgeously  verdant  vegetation 
of  a  forest  of  mammoth  trees,  might  have  ap- 
peared a  somewhat  far  cry  in  the  eyes  of  those 
who  lived  some  fifty  years  ago.  But  there  are 
few  now  who  do  not  know  what  was  the  origin  of 
the  coal  which  they  use  so  freely,  and  which  in 
obedience  to  their  demand  has  been  brought  up 
more  than  a  thousand  feet  from  the  bowels  of  the 
earth ;  and,  although  familiarity  has  in  a  sense 
bred  contempt  for  that  which  a  few  shillings  will 
always  purchase,  in  all  probability  a  stray  thought 
does  occasionally  cross  one's  mind,  giving  birth 
to  feelings  of  a  more  or  less  thankful  nature  that 
such  a  store  of  heat  and  light  was  long  ago  laid 
up  in  this  earth  of  ours  for  our  use,  when  as  yet 
man  was  not  destined  to  put  in  an  appearance  for 
many,  many  ages  to  come.  We  can  scarcely  im- 
agine the  industrial  condition  of  England  in  the 
absence  of  so  fortunate  a  supply  of  coal ;  and  the 
many  good  things  which  are  obtained  from  it,  and 
the  uses  to  which,  as  v/e  shall  see,  it  can  be  put, 
do  indeed  demand  recognition. 


10  THE   STORY  OF  A   PIECE  OF  COAL. 

Were  our  present  forests  uprooted  and  over- 
thrown, to  be  covered  by  sedimentary  deposits 
such  as  those  which  cover  our  coal-seams,  the 
amount,  of  coal  which  would  be  thereby  formed 
for  use  in  some  future  age,  would  amount  to  a 
thickness  of  perhaps  two  or  three  inches  at  most, 
and  yet,  in  one  coal-field  alone,  that  of  West- 
phalia, the  117  most  important  seams,  if  placed 
one  above  the  other  in .  immediate  succession, 
would  amount  to  no  less  than  294  feet  of  coal. 
From  this  it  is  possible  to  form  a  faint  idea  of  the 
enormous  growths  of  vegetation  required  to  form 
some  of  our  representative  coal-beds.  But  the 
coal  is  not  found  in  one  continuous  bed.  These 
numerous  seams  of  coal  are  interspersed  between 
many  thousands  of  feet  of  sedimentary  deposits, 
the  whole  of  which  form  the  "  coal-measures." 
Now,  each  of  these  seams  represents  the  growth 
of  a  forest,  and  to  explain  the  whole  series  it  is 
necessary  to  suppose  that  between  each  deposit 
the  land  became  overwhelmed  by  the  waters  gf 
the  sea  or  lake,  and  after  a  long  sub-aqueous 
period,  was  again  raised  into  dry  land,  ready  to 
become  the  birth-place  of  another  forest,  which 
would  again  beget,  under  similarly  repeated  con- 
ditions, another  seam  of  coal.  Of  the  conditions 
necessary  to  bring  these  changes  about  we  will 
speak  later  on,  but  this  instance  is  sufficient  to 
show  how  inadequate  the  quantity  of  fuel  would 
be,  were  we  dependent  entirely  on  our  own  exist- 
ing forest  growths. 

However,  we  will  leave  for  the  present  the 
fascinating  pursuit  of  theorising  as  to  the  how- 
and  wherefore  of  these  vast  beds  of  coal,  rele- 
gating the  geological  part  of  the  study  of  the  car- 
boniferous system  to  a  future  chapter,  where  will 


THE  ORIGIN  AND   COMPOSITION  OF  COAL.      1 1 

be  found  some  more  detailed  account  of  the  posi- 
tion of  the  coal-seams  in  the  strata  which  contain 
them.  At  present  the  actual  details  of  the  coal 
itself  will  demand  our  attention. 

Coal  is  the  mineral  which  has  resulted,  after 
the  lapse  of  thousands  of  thousands  of  years, 
from  the  accumulations  of  vegetable  material, 
caused  by  the  steady  yearly  shedding  of  leaves, 
fronds  and  spores,  from  forests  which  existed  in 
an  early  age ;  these  accumulated  where  the  trees 
grew  that  bore  them,  and  formed  in  the  first 
place,  perhaps,  beds  ofjDga^;  the  beds  have  since 
been  subjected  to  an  ever-increasing  pressure  of 
accumulating  strata  above  them,  compressing  the 
sheddings  of  a  whole  forest  into  a  thickness  in 
some  cases  of  a  few  inches  of  coal,  and  have  been 
acted  upon  by  the  internal  heat  of  the  earth, 
which  has  caused  them  to  part,  to  a  varying  de- 
gree, with  some  of  their  component  gases.  If  we 
reason  from  analogy,  we  are  compelled  to  admit 
that  the  origin  of  coal  is  due  to  the  accumula- 
tion of  vegetation,  of  which  more  scattered,  but 
more  distinct,  representative  specimens  occur  in 
the  shales  and  clays  above  and  below  the  coal- 
seams.  But  we  are  also  able  to  examine  the 
texture  itself  of  the  various  coals  by  submitting 
extremely  thin  slices  to  a  strong  light  under 
the  microscope,  and  are  thus  enabled  to  decide 
whether  the  particular  coal  we  are  examining 
is  formed  of  conifers,  horse-tails,  club-mosses,  or 
ferns,  or  whether  it  consists  simply  of  the  accu- 
mulated sheddings  of  all,  or  perhaps,  as  in  some 
instances,  of  innumerable  spores. 

In  this  way  the  structure  of  coal  can  be  accu- 
rately determined.  Were  we  artificially  to  pre- 
pare a  mass  of  vegetable  substance,  and  covering 


12  THE  STORY  OF  A  PIECE  OF  COAL. 

it  up  entirely,  subject  it  to  great  pressure,  so  that 
but  little  of  the  volatile  gases  which  would  be 
formed  could  escape,  we  might  in  the  course  of 
time  produce  something  approaching  coal,  but 
whether  we  obtained  lignite,  jet,  common  bitumi- 
nous coal,  or  anthracite,  would  depend  upon  the 
possibilities  of  escape  for  the  gases  contained  in 
the  mass. 

Everybody  has  doubtless  noticed  that,  when  a 
stagnant  pool  which  contains  a  good  deal  of  de- 
caying vegetation  is  stirred,  bubbles  of  gas  rise 
to  the  surface  from  the  mud  below.  This  gas  is 
known  as  marsh-gas,  or  light  carburetted  hydro- 
gen, and  gives  rise  to  the  ignis  fatuus  which  hovers 
about  marshy  land,  and  which  is  said  to  lure  the 
weary  traveller  to  his  doom.  The  vegetable  mud 
is  here  undergoing  rapid  decomposition,  as  there 
is  nothing  to  stay  its  progress,  and  no  superposed 
load  of  strata  confining  its  resulting  products 
within  itself.  The  gases  therefore  escape,  and 
the  breaking-up  of  the  tissues  of  the  vegetation 
goes  on  rapidly. 

The  chemical  changes  which  have  taken  place 
in  the  beds  of  vegetation  of  the  caihonifefous. 
epoch,  and  which  have  transformed  it  into  coal, 
are  even  now  but  imperfectly  understood.  All 
we  know  is  that,  under  certain  circumstances,  one 
kind  of  coal  is  formed,  whilst  under  other  condi- 
tions, other  kinds  have  resulted  ;  whilst  in  some 
cases  the  processes  have  resulted  in  the  prepara- 
tion of  large  quantities  of  mineral  oils,  such  as 
naphtha  and  petroleum.  Oils  are  also  artificially 
produced  from  the  so-called  waste-products  of  the 
gas-works,  but  in  some  parts  of  the  world  the 
process  of  their  manufacture  has  gone  on  natu- 
rally, and  a  yearly  increasing  quantity  is  being  util- 


THE   ORIGIN   AND   COMPOSITION   OF  COAL.      13 


ised.  In  England  oil  has  been  pumped  up  from 
the  carboniferous  strata  of  Coalbrook  Dale,  whilst 
in  Sussex  it  has  been  found  in  smaller  quantities, 
where,  in  all  probability,  it  has  had  its  origin  in 
the  lignitic  beds  of  the  Wealden  strata.  Immense 
quantities  are  used  for  fuel  by  the  Russian  steamers 
on  the  Caspian  Sea,  the  Baku  petroleum  wells  be- 
ing a  most  valuable  possession.  In  Sicily,  Persia, 
and;  far  more  important,  in  the  United  States, 
mineral  oils  are 
found  in  great 
quantity. 

In  all  probabil- 
ity coniferous  trees, 
such  as  the  living 
firs,  pines,  larches, 
etc.,  gave  rise  for 
the  most  part  to 
the  mineral  oils. 
The  class  of  living 
coniferae  is  well 
known  for  the  va- 
rious oils  which  it 
furnishes  natural- 
ly, and  for  others 
which  its  represen- 
tatives yield  on  be- 
ing subjected  to 
distillation.  The 
gradually  increas- 
ing amount  of  heat 
which  we  meet  the 
deeper  we  go  be- 
neath the  surface, 
has  been  the  cause 
of  a  slow  and  continuous  distillation,  whilst  the 


FIG.  2. — Annularia  radiata. 
iferotis  sandstone. 


Carbon- 


THE   STORY  OF  A   PIECE   OF  COAL. 


oil  so  distilled  has  found  its  way  to  the  surface  in 
the  shape  of  mineral-oil  springs,  or  has  accumu- 
lated in  troughs  in  the  strata,  ready  for  use,  to  be 
drawn  up  when  a  well  has  been  sunk  into  it. 

The  plants  which  have  gone  to  make  up  the 
coal  are  not  at  once  apparent  to  the  naked  eye. 
We  have  to  search  among  the  shales  and  clays 
and  sandstones  which  enclose  the  coal-seams,  and' 

in  these  we  find  petrified 
specimens  which  ena- 
ble us  to  build  up  in 
our  mind  pictures  of  the 
vegetable  creation  which 
formed  the  jungles  and 
f  orests  of  j:hese  immense- 
ly remote  ages,  and 
which,  densely  packed 
together  on  the  old  for- 
est floor  of  those  days, 
is  now  apparent  to  us  as 
coal. 

A  very  large  propor- 
tion of  the  plants  which 
have  been  found  in  the 
coal-bearing  strata  con- 
sists of  numerous  spe- 
cies ofj[erns,  the  num- 
ber of  actual  species 
which  have  been  found 
preserved  in  the  English 
coals  being  double  the 
number  now  existing  in 
Europe.  The  greater 
part  of  these  do  not 
seem  to  have  been  very  much  larger  than  our 
own  living  ferns,  and,  indeed,  many  of  them  bear 


FIG.  3. — Rhacopteris  inczquilat- 
era.     Carboniferous  limestone. 


THE  ORIGIN  AND  COMPOSITION   OF  COAL.     15 


a  close  resemblance  to  some  of  our  own  living 
species.  The  impressions  they  have  left  on  the 
shales  of  the  coal-measures,  are  most  striking,  and 
point  to  a  time  when  the  sandy  clay  which  im- 
bedded them  was  borne  by  water  in  a  very  tran- 
quil manner,  to  be  deposited  where  the  ferns  had 
grown,  enveloping  them  gradually,  and  consoli- 
dating them  into  their  mass  of  future  shale.  In 
one  species  known  as  the  neuropteris,  the  nerves 
of  the  leaves  are  as  clear  and  as  apparent  as  in  a 
newly-grown  fern,  the  name  being  derived  from 
two  Greek  words  meaning  "  nerve-fern."  It  is 
interesting  to  consider  the  history  of  such  a  leaf, 
throughout  the  ages  that  have  elapsed  since  it 
was  part  of  a  living  fern.  First  it  grew  up  as  a 
new  frond,  then  gradually  unfolded  itself,  and  de- 
veloped into  the  perfect  fern.  Then  it  became 
cut  off  by  the  rising  waters,  and  buried  beneath 
an  accumulation  of  sediment,  and 
while  momentous  changes  have 
gone  on  in  connection  with  the 
surface  of  the  earth,  it  has  lain 
dormant  in  its  hiding-place  ex- 
actly as  we  see  it,  until  now  exca- 
vated with  its  contemporaneous 
vegetation,  to  form  fuel  for  our 
winter  fires. 

Although  many  of  the  ferns 
greatly  resembled  existing  spe- 
cies, yet  there  were  others  in 
these  ancient  days  utterly  unlike 
anything  indigenous  to  our  coun- 
try now.  There  were  undoubted  tree-ferns,  simi- 
lar to  those  which  thrive  now  so  luxuriously  in 
the  tropics,  and  which  throw  out  their  graceful 
crowns  of  ferns  at  the  head  of  a  naked  stem, 


FIG.   4. — Frond  of 
Pecopteris.    Coal- 
shale. 


1 6  THE  STORY  OF  A  PIECE  OF  COAL. 

whilst  on  the  bark  are  the  marks  at  different 
levels  of  the  points  of  attachment  of  former 
leaves.  These  have  left  in  their  places  cicatrices 
or  scars,  showing  the  places  from  which  they  for- 
merly grew.  Amongst  the  tree-ferns  found  are 
megaphyton,  palceopteris,  and  caulopteris,  all  of  which 
have  these  marks  upon  them,  thus  proving  that 


FIG.  5. — Pecopteris  Serin.     Coal-shale. 

at  one  time  even  tree-ferns  had  a  habitat  in  our 
latitude. 

One  form  of  tree-fern  is  known  by  the  name 


THE  ORIGIN   AND   COMPOSITION   OF   COAL.      17 

of  Psaronius,  and  this  was  peculiar  in  the  posses- 
sion of  masses  of  aerial  roots  grouped  round  the 
stem.  Some  of  the  smaller  species  exhibit  forms 
of  leaves  which  are  utterly  unknown  in  the  nomen- 
clature of  living  ferns.  Most  have  had  names  as- 
signed to  them  in  accordance  with  certain  charac- 
teristics which  they  possess.  This  was  the  more 
possible  since  the  fossilised  impressions  had  been 
retained  in  so  distinct  a  manner.  Here  before  us 
is  a  specimen  in  a  shale  of  pecopteris,  as  it  is  called, 
(pekos,  a  comb).  The  leaf  in  some  species  is  not 
altogether  unlike  the  well-known  living  fern 
osmunda.  The  position  of  the  pinnules  on  both 
sides  of  the  central  stalk  are  seen  in  the  fossil  to 
be  shaped  something  like  a  comb,  or  a  saw,  whilst 
up  the  centre  of  each  pinnule  the  vein  is  as  promi- 
nent and  noticeable  as  if 
the  fern  were  but  yester- 
day waving  gracefully  in 
the  air,  and  but  to-day 
imbedded  in  its  shaly  bed. 
Sphenopteris,  or  "  wedge- 
fern,"  is  the  name  ap- 
plied to  another  coal- 
fern  ;  glossopteriS)  or 
"tongue-leaf  "  ;  cyclopte- 
ris,  or  "  round  -  leaf  "  ; 
odontoptcris,  or  "  tooth- 
leaf,"  and  many  others, 
show  their  chief  charac- 
teristics in  the  names 
which  they  individually 
bear.  Alethopteris  appears 
to  have  been  the  com- 
mon brake  of  the  coal-period,  and  in  some  re- 
spects resembles  pecopteris. 


FIG.   6. — Sphenopteris  affinis. 
Coal-shale. 


1 8  THE   STORY  OF  A   PIECE   OF   COAL. 

In  some  species  of  ferns  so  exact  are  the  rep- 
resentations which  they  have  impressed  on  the 
shale  which  contains  them,  that  not  only  are  the 
veins  and  nerves  distinctly  visible,  but  even  the 
fructification  still  remains  in  the  shape  of  the 
marks  left  by  the  so-called  seeds  on  the  backs  of 
the  leaves.  Something  more  than  a  passing  look 
at  the  coal  specimens  in  a  good  museum  will  well 
repay  the  time  so  spent. 

What  are  known  as  septarian  nodules,  or 
snake-stones,  are,  at  certain  places,  common  in 
the  carboniferous  strata.  They  are  composed  of 
layers  of  ironstone  and  sandstone  which  have 
segregated  around  some  central  object,  such  as 
a  fern-leaf  or  a  shell.  When  the  leaf  of  a  fern 
has  been  found  to  be  the  central  object,  it  has 
been  noticed  that  the  leaf  can  sometimes  be  sepa- 
rated from  the  stone  in  the  form  of  a  carbonace- 
ous film. 

Experiments  were  made  many  years  ago  by 
M.  Goppert  to  illustrate  the  process  of  fossilira- 
tion  of  ferns.  Having  placed  some  living  ferns 
in  a  mass  of  clay  and  dried  them,  he  exposed 
them  to  a  red  heat,  and  obtained  thereby  striking 
resemblances  to  fossil  plants.  According  to  the 
degree  of  heat  to  which  they  were  subjected,  the 
plants  were  found  to  be  either  brown,  a  shining 
black,  or  entirely  lost.  In  the  last  mentioned 
case,  only  the  impression  remained,  but  the  car- 
bonaceous matter  had  gone  to  stain  the  surround- 
ing clay  black,  thus  indicating  that  the  dark  col- 
our of  the  coal-shales  is  due  to  the  carbon  derived 
from  the  plants  which  they  included. 

Another  very  prominent  member  of  the  vege- 
tation of  the  coal-period,  was  that  order  of  plants 
known  as  the  Catamites.  The  generic  distinc- 


THE   ORIGIN  AND   COMPOSITION  OF  COAL.      19 

tions   between    fossil    and    living    ferns  were   so 
slight  in   many   cases  as  to  be  almost  indistin- 


FIG.  7.— Root  of  Calamites  Suckowii.    Coal-shale. 

guishable.  This  resemblance  between  the  ancient 
and  the  modern  is  not  found  so  apparent  in  other 
plants.  The  Calamites  of  the  coal-measures  bore 
indeed  a  very  striking  resemblance,  and  were 


20  THE  STORY   OF  A   PIECE   OF  COAL. 

closely  related,  to  our  modern  horse-tails,  as  the 
equiseta  are  popularly  called  ;  but  in  some  respects 
they  differed  considerably. 

Most  people  are  acquainted  with  the  horse- 
tail (equisctinn  flu- 
viatile)  of  our 
marshes  and  ditch- 
es. It  is  a  some- 
what graceful 
plant,  and  stands 
erect  with  a  joint- 
ed stem.  The  fo- 
liage is  arranged 
in  whorls  around 
the  joints,  and,' 
unlike  its  fossil 
representatives,  its 
joints  are  pro- 
tected by  striated 
sheaths.  The  stem 
of  the  largest  liv- 
*n£  species  rarely 
exceeds  half  an 
inch  in  diameter, 
whilst  that  of  the 

FiG.  8. — Calamoclaaus  grandis.  .  .        . 

Carboniferous  sandstone.  Calamite      attained 

a  thickness  of  five 

inches.  But  the  great  point  which  is  noticeable 
in  the  fossil  calamites  and  equisetites  is  that  they 
grew  to  a  far  greater  height  than  any  similar 
plant  now  living,  sometimes  being  as  much  as 
eight  feet  high.  In  the  nature  of  their  stems, 
too,  they  exhibited  a  more  highly  organised  ar- 
rangement than  their  living  representatives,  hav- 
ing, according  to  Dr.  Williamson,  a  "  fistular  pith, 
an  exogenous  woody  stem,  and  a  thick  smooth 


i^- 


THE   ORIGIN  AND   COMPOSITION   OF  COAL.      21 

bark."  The  bark  having  almost  always  disap- 
peared has  left  the  fluted  stem  known  to  us  as 
the  calamite.  The  foliage  consisted  of  whorls  of 
long  narrow  leaves,  which  differed  only  from  the 
fern  asterophyllites  in  the  fact  that  they  were  sin- 
gle-nerved. Sir  William  Dawson  assigns  the  cala- 
mites  to  four  sub-types:  calamite  proper,  calamo- 
pitus,  c  alamo  dendr  on,  and  encalamodendron. 

Having  used  the  word  "  exogenous,"  it  might 
be  as  well  to  pay  a  little  attention,  in  passing,  to 
the  nomenclature  and  broad  classification  of  the 
various  kinds  of  plants.  We  shall  then  doubtless 
find  it  far  easier  thoroughly  to  understand  the 
position  in  the  scale  of  organisation  to  which  the 
coal  plants  are  referable. 

The  plants  which  are  lowest  in  organisation 
are  known  as  Cellular,  since  they  are  almost  en- 
tirely composed  of  numerous  cells  built  up  one 


FIG.  9. — Asterophyllites  foliosa.     Coal-measures. 


THE   STORY  OF  A   PIECE    OF   COAL. 


above  the  other,  and  possess  none  of  the  higher 
forms  of  tissue  and  organisation  which  are  met 
with  elsewhere.  This  division  includes  the  lich- 
ens, sea-weeds,  confervae  (green  aquatic  scum), 
fungi  (mushrooms,  dry-rot),  &c. 

The  division  of  Vascular  plants  includes  the 
far  larger  proportion  of  vegetation,  both  living 
and  fossil,  and  these  plants  are  built  up  of  vessels 
and  tissues  of  various  shapes  and  character. 

All  plants  are  divided  into  (i)  Cryptogams,  or 
Flowerless,  such  as  mosses,  ferns,  equisetums,  (2) 
Phanerogams,  or  Flowering.  Flowering  plants 
are  again  divided  into  those  with  naked  seeds,  as 
the  conifers  and  cycads  (gymnosperms),  and 
those  whose  seeds  are  enclosed  in  vessels,  or  ova- 
ries (angiosperms). 

Angiosperms  are  again  divided  into  the  mono- 
cotyledons, as  the  palms,  and  dicotyledons,  which 
include  most  trees  of  temperate  regions. 
Thus:— 


(M.  A.  Brongniart). 

(Lindley). 

CELLULAR 

Cryptogams  (Flowerless) 

Fungi,     seaweeds, 

Thallogens 

lichens 

VASCULAR 

Cryptogams  (Flowerless) 

Ferns,  equisetums, 

Acrogens 

mosses,    lycopo- 

diums 

Phanerogams  (Flowering) 

Gymnosperms  (having 

Conifers   and    cy- 

Gymnogens 

naked  seeds) 

cads 

i.  Dicotyledons 

Angiosperms   (having 

enclosed  seeds) 

i.  Monocotyledons 

Palms,            lilies, 

Endogens 

grasses 

ii.  Dicotyledons 

Most       European 

Exogens 

trees  and  shrubs 

THE  ORIGIN   AND   COMPOSITION   OF  COAL.      23 

Adolphe  Brongniart  termed  the  coal  era  the 
•*  Age  of  Acrogens,"  because,  as  we  shall  see,  of 
the  great  predominance  in  those  times  of  vascular 
cryptogamic  plants,  known  in  Dr.  Lindley's  no- 
menclature as  "  Acrogens." 

Two  of  these  families  h^ve  already  been  dealt 
with,  viz.,  the  ferns  (filices),  and  the  equisetums, 
(calamites  and 
equisetites) ,  and 
we  now  have  to 
pass  on  to  an- 
other family. 
This  is  that 
which  includes 
the  fossil  repre- 
sentatives of  the 
Lycopodiums,  or 
Club  -  mosses, 
and  which  goes 
to  make  up  in 
some  coals  as 
much  as  two- 
thirds  of  the 
whole  mass. 
Everyone  is 

more  or  less  familiar  with  some  of  the  living 
Lycopodiums,  those  delicate  little  fern-like  mosses 
which  are  to  be  found  in  many  a  home.  They 
are  but  lowly  members  of  our  present  flora,  and 
it  may  seem  somewhat  astounding  at  first  sight 
that  their  remote  ancestors  occupied  so  important 
a  position  in  the  forests  of  the  ancient  period  of 
which  we  are  speaking.  Some  two  hundred  liv- 
ing species  are  known,  most  of  them  being  con- 
fined to  tropical  climates.  They  are,  as  a  rule, 
low  creeping  plants,  although  some  few  stand 


FIG.  10. — Sphenophyllum  cuneifolium. 
Coal  shale. 


THE   STORY   OF  A   PIECE   OF   COAL. 


erect.  There  is  room  for  astonishment  when  we 
consider  the  fact  that  the  fossil  representatives  of 
the  family,  known  as  Lepidodendra,  attained  a 
height  of  no  less  than  fifty  feet,  and  there  is  good 
ground  for  believing,  in  many  cases,  a  far  greater 
magnitude.  They  consist  of  long  straight  stems, 
or  trunks  which  branch  considerably  near  the  top. 
These  stems  are  covered  with  scars  or  scales, 
which  have  been  caused  by  the  separation  of  the 
petioles  or  leaf-stalks,  and  this  gives  rise  to  the 
name  which  the  genus  bears.  The  scars  are  ar- 
ranged in  a  spiral  manner  the  whole  of  the  way 
up  the  stem,  and  the  stems  often  remain  perfectly 
upright  in  the  coal-mines,  and  reach  into  the 
strata  which  have  accumulated 
above  the  coal-seam. 

Count  Sternberg  remarked 
that  we  are  unacquainted  with 
any  existing  species  of  plant, 
which  like  the  Lepidodendron,  pre- 
serves at  all  ages,  and  throughout 
the  whole  extent  of  the  trunk, 
the  scars  formed  by  the  attach- 
ment of  the  petioles,  or  leaf- 
stalks, or  the  markings  of  the 
leaves  themselves.  The  yucca, 
dracaena,  and  palm,  entirely  shed 
their  scales  when  they  are  dried 
up,  and  there  only  remain  cir- 
cles, or  rings,  arranged  round  the 
trunk  in  different  directions.  The 
flabelliform  palms  preserve  their 
scales  at  the  inferior  extremity 
of  the  trunk  only,  but  lose  them  as  they  increase 
in  age  ;  and  the  stem  is  entirely  bare,  from  the 
middle  to  the  superior  extremity.  In  the  ancient 


FIG.  n.— Cast  of 

Lepidodendron  in 
sandstone. 


THE   ORIGIN   AND   COMPOSITION   OF  COAL.      25 


FIG.   12. — Lepidodendron  longifolium. 
Coal-shale. 


Lepidodendron,  on  the  other  hand,  the  more  an- 
cient the  scale  of  the  leaf-stalk,  the  more  appar- 
ent it  still  re- 
mains. Portions 
of  stems  have 
been  discovered 
which  contain 
leaf  -  scars  far 
larger  than  those 
referred  to  above, 
and  we  deduce 
from  these  frag- 
ments the  fact 
that  those  indi- 
viduals which 
have  been  found 
whole,  are  not  by  any  means  the  largest  of  those 
which  went  to  form  so  large  a  proportion  of  the 
ancient  coal-forests.  The  lepidodendra  bore  linear 
one-nerved  leaves,  and  the 
stems  always  branched  di- 
chotomously  and  possessed 
a  central  pith.  Specimens 
variously  named  knorrta, 
lepidophloios i  halonia,  and  ulo- 
dendron  are  all  referable  to 
this  family. 

In  some  strata,  as  for 
instance  that  of  the  Shrop- 
shire coal-field,  quantities 
of  elongated  cylindrical 
bodies  known  as  lepidostrobi 
have  been  found,  which,  it 
was  early  conjectured,  were 
the  fruit  of  the  giant  club-mosses  about  which  we 
have  just  been  speaking.  Their  appearance  can 


FIG.  13. — Lepidodendron 
aculeatum  in  sandstone. 


26 


THE   STORY  OF  A   PIECE  OF  COAL. 


be  called  to  mind  by  imagining  the  cylindrical 
fruit  of  the  maize  or  Indian  corn  to  be  reduced  to 
some  three  or  four  inches  in  length.  The  spo- 
rangia or  cases  which  contained  the  microscopic 
spores  or  seeds  were  arranged  around  a  central 
axis  in  a  somewhat  similar  manner  to  that  in 
which  maize  is  found.  These  bodies  have  since 
been  found  actually  situated  at  the  end  of 
branches  of  lepidodendron, 
thus  placing  their  true 
nature  beyond  a  doubt. 
The  fossil  seeds  (spores) 
do  not  appear  to  have  ex- 
ceeded in  volume  those 
of  recent  club-mosses, 
and  this  although  the  ac- 
tual trees  themselves 
grew  to  a  size  very  many 
times  greater  than  the 
living  species.  This  mi- 
nuteness of  the  seed- 
germs  goes  to  explain  the 
reason  why,  as  Sir  Charles 
Lyell  remarked,  the  same 
species  of  lepidodendra  are 
so  widely  distributed  in 
the  coal  measures  of  Eu- 
rope and  America,  their 
spores  being  capable  of 
an  easy  transportation  by  the  wind. 

One  striking  feature  in  connection  with  the 
fruit  of  the  lepidodendron  and  other  ancient  repre- 
sentatives of  the  club-moss  tribe,  is  that  the  bitu-' 
minous  coals  in  many,  if  not  in  most,  instances, 
are  made  up  almost  entirely  of  their  spores  and 
spore-cases.  Under  a  microscope  a  piece  of  such 


FIG.  14. — Lepidostrobus. 
Coal-shale. 


THE  ORIGIN   AND   COMPOSITION   OF   COAL.     27 

coal  is  seen  to  be  thronged  with  the  minute 
rounded  bodies  of  the  spores  interlacing  one  an- 
other and  forming  almost  the  whole  mass,  whilst 
larger  than  these,  and  often  indeed  enclosing 
.  them,  are  flattened  bag-like  bodies  which  are 
none  other  than  the  compressed  sporangia  which 
contained  the  former. 

Now,  the  little  Scottish  or  Alpine  club-moss 
which  is  so  familiar,  produces  its  own  little  cones, 


FIG.  15. — Lycopodites.    Coal  sandstone. 

each  with  its  series  of  outside  scales  or  leaves ; 
these  are  attached  to  the  bags  or  spore-cases, 
which  are  crowded  with  spores.  Although  in 
miniature,  yet  it  produces  its  fruit  in  just  the 
same  way,  at  the  terminations  of  its  little  branches, 
and  the  spores,  the  actual  germs  of  life,  when  ex- 
amined microscopically,  are  scarcely  distinguish- 
able from  those  which  are  contained  in  certain 
bituminous  coals.  And,  although  ancient  club- 
mosses  have  been  found  in  a  fossilised  condition 
at  least  forty-nine  feet  high,  the  spores  are  no 


\28  THE   STORY   OF  A   PIECE  OF  COAL. 

larger  than  those  of  the  miniature  club-mosses  of 
the  present  day. 

The  spores  are  more  or  less  composed  of  pure 
bitumen,  and  the  bituminous  nature  of  the  ct>al 
depends  largely  on  the  presence  or  absence  of 
these  microscopic  bodies  in  it.  The  spores  of 
the  living  club-mosses  contain  so  much  resinous 
matter  that  they  are  now  largely  used  in  the 
making  of  fireworks,  and  upon  the  presence  of 
this  altered  resinous  matter  in  coal  depends  its 
capability  of  providing  a  good  blazing  coal. 

At  first  sight  it  seems  almost  impossible  that 
such  a  minute  cause  should  result  in  the  forma- 
tion of  huge  masses  of  coal,  such  an  inconceivable 
number  of  spores  being  necessary  to  make  even 
the  smallest  fragment  of  coal.  But  if  we  look  at 
the  cloud  of  spores  that  can  be  shaken  from  a 
single  spike  of  a  club-moss,  then  imagine  this  to 
be  repeated  a  thousand  times  from  each  branch 
of  a  fairly  tall  tree,  and  then  finally  picture  a 
whole  forest  of  such  trees  shedding  in  due  sea- 
son their  copious  showers  of  spores  to  earth,  we 
shall  perhaps  be  less  amazed  than  we  were  at  first 
thought,  at  the  stupendous  result  wrought  out  by 
so  minute  an  object. 

/  Another  well-known  form  of  carboniferous 
vegetation  is  that  known  as  the  Sigillaria,  and, 
connected  with  this  form  is  one,  which  was  long 
familiar  under  the  name  of  Stigmaria,  but  which 
has  since  been  satisfactorily  proved  to  have 
formed  the  branching  root  of  the  sigillaria.  The 
older  geologists  were  in  the  habit  of  placing 
these  plants  among  the  tree-ferns,  principally  on 
account  of  the  cicatrices  which  were  left  at  the 
junctions  of  the  leaf-stalks  with  the  stem,  after 
the  former  had  fallen  off.  No  foliage  had,  how- 


THE  ORIGIN   AND   COMPOSITION   OF   COAL.      29 

ever,  been  met  with  which  was  actually  attached 
to  the  plants,  and  hence,  when  it  was  discovered 
that  some  of  them  had  long  attenuated  leaves 
not  at  all  like  those  possessed  by  ferns,  geologists 
were  compelled  to  abandon  this  classification  of 
them,  and  even  now  no  satisfactory  reference  to 
existing  orders  of  them  has  been  made,  owing  to 
their  anomalous  structure.  The  stems  are  fluted 
from  base  to  stem,  although  this  is  not  so  appar- 
ent near  the  base,  whilst  the  raised  prominences 
which  now  form  the  cicatrices,  are  arranged  at 
regular  distances  within  the  vertical  grooves. 

When  they  have  remained  standing  for  some 
length  of  time,  and  the  strata  have  been  allowed 
quietly  to  accumulate  around  the  trunks,  they 
have  escaped  compression.  They  were  evident- 
ly, to  a  great  extent,  hollow  like  a  reed,  so  that 
in  those  trees  which  still  remain  vertical,  the  in- 
terior  has  become  filled  up  by  a  coat  of  sand- 
stone, whilst  the  bark  has  become  transformed 
into  an  envelope  of  an  inch,  or  half  an  inch  of 
coal.  But  many  are  found  lying  in  the  strata  in 
a  horizontal  plane.  These  have  been  cast  down 
and  covered  up  by  an  ever-increasing  load  of 
strata,  so  that  the  weight  has,  in  the  course  of 
time,  compressed  the  tree  into  simply  the  thick- 
ness of  the  double  bark,  that  is,  of  the  two 
opposite  sides  of  the  envelope  which  covered  it 
when  living. 

SigUlaritz  grew  to  a  very  great  height  without 
branching,  some  specimens  having  measured  from 
60  to  70  feet  long.  In  accordance  with  their 
outside  markings,  certain  types  are  known  as 
syringodendron,  favularia,  and  clathraria.  Dip- 
loxylon  is  a  term  applied  to  an  interior  stem  ref- 
erable to  the  family. 


30  THE   STORY  OF  A   PIECE  OF  COAL. 

But  the  most  interesting  point  about  the 
sigillaricR  is  the  root.  This  was  for  a  long  time 
regarded  as  an  entirely  distinct  individual,  and 
the  older  geologists  explained  it  in  their  writings 


FIG.  \6.—Stigmariaficoides.    Coal-shale. 

as  a  species  of  succulent  aquatic  plant,  giving  it 
the  name  of  stigmaria.  They  realized  the  fact 
that  it  was  almost  universally  found  in  those  beds 
which  occur  immediately  beneath  the  coal-seams, 
but  for  a  long  time  it  did  not  strike  them  that  it 
might  possibly  be  the  root  of  a  tree.  In  an 
old  edition  of  Lyell's  "  Element's  of  Geology," 
utterly  unlike  existing  editions  in  quality,  quan- 
tity, or  comprehensivene:s,  after  describing  it  as 
an  extinct  species  of  water-plant,  the  author 
hazarded  the  conjecture  that  it  might  ultimately 
be  found  to  have  a  connection  with  some  other 
well-known  plant  or  tree.  It  was  noticed  that 
above  the  coal,  in  the  roof,  stigmariae  were 
absent,  and  that  the  stems  of  trees  which  oc- 
curred there  had  become  flattened  by  the  weight 
of  the  overlying  strata.  The  stigmarise,  on 
the  other  hand,  abounded  in  the  underday^  as  it 


THE  ORIGIN  AND   COMPOSITION  OF   COAL.      31 

is  called,  and  were  not  in  any  way  compressed 
but  retained  what  appeared  to  be  their  natural 
shape  and  position.  Hence  to  explain  their 
appearance,  it  was  thought  that  they  were  water- 
plants,  ramifying  the  mud  in  every  direction,  and 
finally  becoming  overwhelmed  and  covered  by 
the  mud  itself.  On  botanical  grounds,  Brongniart 
and  Lyell  conjectured  that  they  formed  the  roots 
of  other  trees,  and  this  became  the  more  appar- 
ent as  it  came  to  be  acknowledged  that  the  un- 
derclays  were  really  ancient  soils.  All  doubt 
was,  however,  finally  dispelled  by  the  discovery 
by  Mr.  Binney,  of  a  sigillaria  and  a  stigmaria  in 
actual  connection  with  each  other,  in  the  Lanca- 
shire coal-field. 

Stigmariae  have  since  been  found  in  the  Cape 
Breton  coal-field,  attached  to  Lepidodendra,  about 
which  we  have  already  spoken,  and  a  similar  dis- 
covery has  since  been  made  in  the  British  coal- 
fields. This,  therefore,  would  seem  to  show  the 
affinity  of  the  sigillaria  to  the  lepidodendron, 
and  through  it  to  the  living  lycopods,  or  club- 
mosses. 

Some  few  species  of  stigmarian  roots  had  been 
discovered,  and  various  specific  names  had  been 
given  to  them  before  their  actual  nature  was 
made  out.  What  for  some  time  were  thought  to 
be  long  cylindrical  leaves,  have  now  been  found 
to  be  simply  rootlets,  and  in  specimens  where 
these  have  been  removed,  the  surface  of  the  stig- 
maria has  been  noticed  to  be  covered  with  large 
numbers  of  protuberant  tubercles,  which  have 
formed  the  bases  of  the  rootlets.  There  appears 
to  have  also  been  some  special  kind  of  arrange- 
ment in  their  growth,  since,  unlike  the  roots  of 
most  living  plants,  the  tubercles  to  which  these 


THE  STORY  OF  A   PIECE  OF   COAL. 


FIG.  17. — Section  of  stigmaria. 


rootlets   were* attached,   were    arranged    spirally 
around  the  main  root.     Each    of  these  tubercles 

was  pitted  in  the 
centre,  and  into 
these  the  almost 
pointed  ends  of  the 
rootlets  fitted  as  by 
a  ball  and  socket 
joint. 

UA  single  trunk 
of  si  gill  aria  in  an 
erect  forest  pre- 
sents an  epitome  of 
a  coal-seam.  Its 
roots  represent  the 
stigmaria  under- 
day  ;  its  bark  the 
compact  coal ;  its  woody  axis  the  mineral  char- 
coal ;  its  fallen  leaves  and  fruits,  with  remains  of 
herbaceous  plants  growing  in  its  shade,  mixed 
with  a  little  earthy  matter,  the  layers  of  coarse 
coal.  The  condition  of  the  durable  outer  bark  of 
erect  trees,  concurs  with  the  chemical  theory  of 
coal,  in  showing  the  especial  suitableness  of  this 
kind  of  tissue  for  the  production  of  the  purer 
compact  coals." — Dawson,  "  Structures  in  Coal." 
There  is  yet  one  other  family  of  plants  which 
must  be  mentioned,  and  which  forms  a  very  im- 
portant portion  of  the  constituent  floza-Qi  the  coal- 
period.  This  is  the  great  family  of  the  conifer  a, 
which  although  differing  in  many  respects  from 
the  highly  organised  dicotyledons  of  the  present 
day,  yet  resembled  them  in  some  respects,  espe- 
cially in  the  formation  of  an  annual  ring  of  woody 
growth. 

The   conifers   are   those    trees   which,   as   the 


THE   ORIGIN   AND  COMPOSITION   OF   COAL.      33 

name  would  imply,  bear  their  fruit  in  the  form 
of  cones,  such  as  the  fir,  larch,  cedar,  and  others. 
The  order  is  one  which  is  familiar  to  all,  not 
only  on  account  of  the  cones  they  bear,  and  their 
sheddings,  which  in  the  autumn  strew  the  ground 
with  a  soft  carpet  of  long  needle-like  leaves,  but 
also  because  of  the  gum-like  secretion  of  resin 
which  is  contained  in  their  tissues.  Only  a  few 
species  having  been  found  in  the  coal-beds,  and 
these,  on  examination  under  the  microscope,  have 
been  discovered  to  be  closely  related  to  the  arau- 
carian  division  of  pines,  rather  than  to  any  of 
our  common  firs.  The  living  species  of  this 
tree  is  a  native  of  Norfolk  Island,  in  the  Pacific, 
and  here  it  attains  a  height  of  200  feet,  with  a 
girth  of  30  feet.  From  the  peculiar  arrangement 
of  the  ducts  in  the  elongated  cellular  tissue  of 
the  tree,  as  seen  under  the  microscope,  the  fossil 
conifers,  which  exhibit  this  structure,  have  been 
placed  in  the  same  division. 

The  familiar  fossil  known  to  geologists  as 
Sternbergia  has  now  been  shown  to  be  the  cast  of 
the  central  pith  of  these  conifers,  amongst  which 
may  be  mentioned  cordaites,  araucarites,  and  dad- 
oxylon.  The  central  cores  had  become  replaced 
with  inorganic  matter  after  the  pith  had  shrunk 
and  left  the  space  empty.  This  shrinkage  of  the 
pith  is  a  process  which  takes  place  in  many  plants 
even  when  living,  and  instances  will  at  once  occur, 
~in  which  the  stems  of  various  species  of  shrubs 
when  broken  open  exhibit  the  remains  of  the 
shrunken  pith,  in  the  shape  of  thin  discs  across 
the  interval  cavity. 

We  might  reasonably  expect  that  where  we 
find  the  remains  of  fossil  coniferous  trees,  we 
should  also  meet  with  the  cones  or  fruit  which 


34  THE   STORY   OF  A   PIECE   OF   COAL. 

they  bear.  And  such  is  the  case.  In  some  coal- 
districts  fossil  fruits,  named  cardiocarpum  and 
trigonocarpum,  have  been  found  in  great  quanti- 
ties, and  these  have  now  been  decided  by  bot- 
anists to  be  the  fruits  of  certain  conifers,  allied, 
not  to  those  which  bear  hard  cones,  but  to  those 
which  bear  solitary  fleshy  fruits.  Sir  Charles 
Lyell  referred  them  to  a  Chinese  genus  of  the 
yew  tribe  called  salisburia.  Dawson  states  that 
they  are  very  similar  to  both  taxus  and  salisburia. 
They  are  abundant  in  some  coal-measures,  and 
are  contained,  not  only  in  the  coal  itself,  but  also 
in  the  sandstones  and  shales.  The  under-clays 
appear  to  be  devoid  of  them,  and  this  is,  of  course, 
exactly  what  might  have  been  expected,  since  the 
seeds  would  remain  upon  the  soil  until  covered  up 
by  vegetable  matter,  but  would  never  form  part 
of  the  clay  soil  itself. 

In  connection  with  the  varieties  which  have 
been  distinguished  in  the  families  of  the  conifers, 
calamites,  and  sigillariae,  Sir  William*  Dawson 
makes  the  following  observations :  "  I  believe 
that  there  was  a  considerably  wide  range  of  or- 
ganisation in  cordaitina  as  well  as  in  calamites  and 
sigillarice,  and  that  it  will  eventually  be  found  that 
there  were  three  lines  of  connection  between  the 
higher  cryptogams  (flowerless)  and  the  phaeno- 
gams  (flowering),  one  leading  from  the  lycopodes 
by  the  sigillarice,  another  leading  by  the  cordaites, 
and  the  third  leading  from  the  equisetums  by  the 
calamites.  Still  further  back  the  characters,  after- 
wards separated  in  the  club-mosses,  mare's-tails, 
and  ferns,  were  united  in  the  rhizocarps,  or,  as 
some  prefer  to  call  them,  the  heterosporous  Jilt- 
cina" 
/In  concluding  this  chapter  dealing  with  the 


THE   ORIGIN   AND   COMPOSITION   OF   COAL.      35 

various  kinds  of  plants  which  have  been  discov- 
ered as  contributing  to  the  formation  of  coal- 
measures,  it  would  be  as  well  to  say  a  word  or 
two  concerning  the  climate  which  must  have  been 
necessary  to  permit  of  the  growth  of  such  an 
abundance  of  vegetation.  It  is  at  once  admitted) 
by  all  botanists  that  a  moist  and  quite  warm  at-\ 
mosphere  was  necessary  to  account  for  the  exist- 
ence of  such  an  abundance  of  ferns.  The  gor*J 
geous  waving  tree-ferns  which  were  doubtless  an 
important  feature  of  the  landscape,  would  have 
required  a  moist  heat  such  as  does  not  now  exist 
in  this  latitude,  although  not  necessarily  a  trop- 
ical heat.  The  magnificent  giant  lycopodiums 
cast  into  the  shade  all  our  living  members  of  that 
class,  the  largest  of  which  perhaps  are  those  that 
flourish  in  New  Zealand.  In  New  Zealand,  too, 
are  found  many  species  of  ferns,  both  those  which 
are  arborescent  and  those  which  are  of  more  hum- 
ble stature.  Add  to  these  the^numerous  conifers 
which  are  there  found,  and  we  shall  find  that  a 
forest  in  that  country  may  represent  to  a  certain 
extent  the  appearance  presented  by  a  forest  of 
carboniferous  vegetation.  The  ferns,  lycopods, 
and  pines,  however,  which  appear  there,  it  is  but 
fair  to  add,  are  mixed  with  other  types  allied  to 
more  recent  forms  of  vegetation. 

There  are  many  reasons  for  believing  that  the 
amount  of  carbonic  acid  gas  then  existing  in  the 
atmosphere  was  larger  than  the  quantity  which 
we  now  find,  and  Professor  Tyndall  has  shown 
that  the  effect  of  this  would  be  to  prevent  radia- 
tion of  heat  from  the  earth.  The  resulting  forms 
of  vegetation  would  be  such  as  would  be  com- 
parable with  those  which  are  now  reared  in  the 
green-house  or  conservatory  in  these  latitudes. 


36  THE   STORY   OF   A   PIECE   OF   COAL. 

The  gas  would,  in  fact,  act  as  a  glass  roof,  ex- 
tending over  the  whole  world. 


CHAPTER   II. 

A  GENERAL  VIEW    OF   THE   COAL-BEARING   STRATA. 

IN  considering  the  source  whence  coal  is  de- 
rived, we  must  be  careful  to  remember  that  coal 
itself  is  but  a  minor  portion  of  the  whole  forma- 
tion in  which  it  occurs.  The  presence  of  coal  has 
indeed  given  the  name  to  the  formation,  the  wrord 
"carboniferous"  meaning  "coal-bearing,"  but  in 
taking  a  comprehensive  view  of  the  position  which 
it  occupies  in  the  bowels  of  the  earth,  it  will  be 
necessary  to  take  into  consideration  the  strata  in 
which  it  is  found,  and  the  conditions,  so  far  as  are 
known,  under  which  these  were  deposited. 

Geologically  speaking,  the  Carboniferous  for- 
mation occurs  near  the  close  of  that  group  of  sys- 
tems which  have  been  classed  as  "  palaeozoic," 
younger  in  point  of  age  than  the  well-known  De- 
vonian and  Old  Red  Sandstone  strata,  but  older 
by  far  than  the  Oolites,  the  Wealden,  or  the  Cre- 
taceous strata. 

In  South  Wales  the  coal-bearing  strata  have 
been  estimated  at  between  11,000  and  12,000  feet, 
yet  amongst  this  enormous  thickness  of  strata,  the 
whole  of  the  various  coal-seams,  if  taken  together, 
probably  does  not  amount  to  more  than  120  feet. 
This  great  disproportion  between  the  total  thick- 
ness and  the  thickness  of  coal  itself  shows  itself 
in  every  coal-field  that  has  been  worked.  The 
thickness  of  single  seams  varies  from  that  of  a 


GENERAL  VIEW  OF  COAL-BEARING  STRATA.  37 

knife-blade  to  over  a  hundred  feet,  the  largest  of 
these  occurring  in  Pennsylvania  and  Southern 
France.  Those  over  eight  or  ten  feet  are  almost 
always  compound  seams — that  is,  they  consist  of 
two  or  more  seams  or  "  benches  "  separated  by 
thin  "  partings,"  which  represent  thicker  strata 
of  clay  or  sandstone  that  have  thinned  out. 

It  is  not  possible,  therefore,  to  realise  complete- 
ly the  significance  of  the  coal-beds  themselves  un- 
less there  is  also  a  knowledge  of  the  remaining 
constituents  of  the  whole  formation.  The  strata 
found  in  the  various  coal-fields  differ  considerably 
amongst  themselves  in  character.  There  are, 
however,  certain  well-defined  characteristics  which 
find  representation  in  most  of  the  principal  coal- 
fields. 

The  following  list,  condensed  from  reports  by 
J.  J.  Stevenson  and  H.  M.  Chance,  gives  a  gen- 
eral idea  of  the  association  of  strata  in  Western 
Pennsylvania : 

UPPER  BARREN  SERIES,  OR  PERMIAN  BEDS. 

Alternating  beds  of  limestone,  sandstone, 
and  shale,  with  one  or  two  feet  in  a 
hundred  of  coal,  and  iron  ore  in  some 
localities. 

UPPER  PRODUCTIVE  COAL  SERIES,  OR  MONON- 
GAHELA  RIVER  SERIES. 

Shale,  sandstone,  limestone,  and  fire-clay 
alternating  with  coal-beds  which  may 
reach  a  proportion  of  i  in  20. 

LOWER  BARREN  COAL-MEASURES. 

Connellsville,  Morgantown,  and  Mahoning 
sandstones,  shale,  black  and  crinoidal 
limestone,  fire-clay  and  coal. 


38  THE   STORY   OF  A   PIECE   OF   COAL. 

LOWER  PRODUCTIVE   COAL-MEASURES,  OR  AL- 
LEGHANY  RlVER  SERIES  : 

Fire-clay,  Freeport  limestone,  shale,  sand- 
stone, brick-clay,  and  slate  in  about  the 
same  proportion  with  coal  as  in  the  Up- 
per Productive  Series. 

Pottsville  conglomerate,  or  millstone  grit. 

Layers  of  clay-ironstone  are  often  in  the  series. 

In  the  Pennsylvania  anthracite  region  about 
the  same  formations  alternate,  except  that  lime- 
stone is  absent. 

S*>\i\  short,  the  formation  consists  of  masses  of 
sandstone,  shale,  limestone,  and  coal,  these  also 
enclosing  clays  and  ironstones,  and,  in  the  lime- 
stone, marbles  and  veins  of  the  ores  of  lead, 
zinc,  and  antimony,  and  occasionally  silver. 

Each  of  the  principal  divisions  has  its  repre- 
sentative in  Great  Britain,  Belgium,  and  Ireland, 
but,  unfortunately  for  the  last-named  country, 
the  whole  of  the  upper  productive-measures  are 
there  absent.  It  is  from  these  measures  that 
almost  all  our  commercial  coals  are  obtained. 

As  the  most  apparent  of  the  rocks  of  the  sys- 
tem are  sandstone^"  shale,  limestone,  and  coal,  it 
will  be  necessary  t<\  consider  how  these  were  de- 
posited in  the  waters  of  the  carboniferous  ages, 
and  this  we  can  best  do  by  considering  the  laws 
under  which  strata  of  a  similar  nature  are  now 
being  deposited  as  sedimentary  beds. 

A  great  proportion  consists  of  sandstone. 
Now  sandstone  is  the  result  of  sand  which  has 
been  deposited  in  large  quantities,  having  be- 
come indurated  or  hardened  by  various  processes 
brought  to  bear  upon  it.  It  is  necessary,  there- 
fore, first  to  ascertain  whence  came  the  sand,  and 


GENERAL  VIEW  OF  COAL-BEARING  STRATA.  39 

whether  there  are  any  peculiarities  in  its  method 
of  deposition  which  will  explain  its  stratification. 
It  will  be  noticed  at  once  that  it  bears  a  considera- 
ble amount  of  evidence  of  what  is  called  "  current- 


FIG.  18. — Sigillarian  trunks  in  current-bedded  sandstone. 
St.  Etienne. 

bedding,"  that  is  to  say,  that  the  strata,  instead  of 
being  regularly  deposited,  exhibit  series  of  wedge- 
shaped  masses,  which  are  constantly  thinning  out. 
Sand  and  quartz  are  of  the  same  chemical 
composition,  and  in  all  probability  the  sand  of 
which  every  sandstone  in  existence  is  composed, 
appeared  on  this  earth  in  its  first  solid  form  in  the 
shape  of  quartz.  Now  quartz  is  a  comparatively 
heavy  mineral,  so  also,  therefore,  will  sand  be. 
It  is  also  very  hard,  and  in  these  two  respects  it 
differs  entirely  from  another  product  of  sedimen- 
tary deposition,  namely,  mud  or  clay,  with  which 


40  THE    STORY   OF   A   PIECE   OF   COAL. 

we  shall  have  presently  to  deal  when  coming  to 
the  shales.  Since  quartz  is  a  hard  mineral,  it 
necessarily  follows  that  it  will  suffer,  without 
being  greatly  affected,  a  far  greater  amount  of 
wearing  and  knocking  about  when  being  trans- 
ported by  the  agency  of  currents  and  rivers,  than 
will  a  softer  substance,  such  as  clay.  An  equal 
amount  of  this  wearing  action  upon  clay  will  re- 
duce it  to  a  fine  impalpable  silt.  The  grains  of 
sand,  however,  will  still  remain  of  an  appreciable 
average  size,  and  where  both  sand  and  clay  are 
being  transported  to  the  sea  in  one  and  the  same 
stream,  the  clay  will  be  transported  to  long  dis- 
tances, whilst  the  sand,  being  heavier,  bulk  for 
bulk,  and  also  consisting  of  grains  larger  in  size 
than  grains  of  clay,  will  be  rapidly  deposited,  and 
form  beds  of  sand.  Of  course,  if  the  current  be 
a  violent  one,  the  sand  is  transported,  not  by 
being  held  in  suspension,  but  rather  by  being 
pushed  along  the  bed  of  the  river  ;  such  an  action 
will  then  tend  to  cause  the  sand  to  become  pow- 
dered into  still  finer  sand. 

When  a  river  enters  a  sea  it  soon  loses  its  in- 
dividuality ;  it  becomes  merged  in  the  body  of 
the  ocean,  where  it  loses  its  current,  and  where 
therefore  it  has  no  power  to  keep  in  suspension 
the  sediment  which  it  had  brought  down  from 
the  higher  lands.  When  this  is  the  case,  the  sand 
borne  in  suspension  is  the  first  to  be  deposited, 
and  this  accumulates  in  banks  near  the  entrance 
of  the  river  into  the  sea.  We  will  suppose,  for 
illustration,  that  a  small  river  has  become  charged 
with  a  supply  of  sand.  As  it  gradually  approaches 
the  sea,  and  the  current  loses  its  force,  the  sand 
is  the  mof^  sluggishly  carried  along,  until  finally 
it  falls  to  the  bottom,  and  forms  a  layer  of  sand 


GENERAL  VIEW  OF  COAL-BEARING  STRATA.     41 

there.  This  layer  increases  in  thickness  until  it 
pauses  the  depth  of  water  above  it  to  become 
comparatively  shallow.  On  the  shallowing  proc- 
ess taking  place,  the  current  will  still  have  a 
certain,  though  slighter,  hold  on  the  sand  in  sus- 
pension, and  will  transport  it  yet  a  little  further 
seaward,  when  it  will  be  thrown  down  at  the  edge 
of  the  bank  or  layer  already  formed,  thus  tend- 
ing to  extend  the  bank,  and  to  shallow  a  wider 
space  of  river-bed. 

As  a  result  of  this  action,  strata  would  be 
formed,  showing  stratification  diagonally  as  well 
as  horizontally,  represented  in  section  as  a  num- 
ber of  banks  which  had  seemingly  been  thrown 
down  one  above  the  other,  ending  in  thin  wedge- 
shaped  terminations  where  the  particular  supply 
of  sediment  to  which  each  owed  its  formation 
had  failed. 

The  masses  of  sandstone  which  are  found  in 
the  carboniferous  formation,  exhibit  in  a  large 
degree  these  wedge-shaped  strata,  and  we  have 
therefore  a  clue  at  once,  both  as  to  their  propin- 
quity to  sea  and  land,  and  also  as  to  the  manner 
in  which  they  were  formed. 

There  is  one  thing  more,  too,  about  them. 
Just  as,  in  the  case  we  were  considering,  we  could 
observe  that  the  wedge-shaped  strata  always 
pointed  away  from  the  source  of  the  material 
which  formed  them,  so  we  can  similarly  judge 
that  in  the  carboniferous  strata  the  same  deduc- 
tion holds  good,  that  the  diagonally-pointing 
strata  were  formed  in  the  same  way,  and  that 
their  thinning  out  was  simply  owing  to  tempo- 
rary failure  of  sediment,  made  good,  hpwever,  by 
a  further  deposition  of  strata  when  the  next  sup- 
ply was  borne  down. 


42  THE  STORY  OF  A   PIECE  OF  COAL. 

It  is  scarcely  likely,  however,  that   sand  in  a 
pure  state  was  always  carried  down  by  the  cur- 

rents to  the  sea.  Some- 
times there  would  be 
some  silt  mixed  with  it. 
Just  as  in  many  parts 
large  masses  of  almost 
pure  sandstone  have 
been  formed,  so  in 
other  places  shales,  or, 
as  they  are  popularly 


. 

Coal-measures.  "bind,         have      been 

formed.       Shales      are 

formed  from  the  clays  which  have  been  carried 
down  by  the  rivers  in  the  shape  of  silt,  but  which 
have  since  become  hardened,  and  now  split  up 
easily  into  thin  parallel  layers.  The  reader  has 
no  doubt  often  handled  a  piece  of  hard  clay  when 
fresh  from  the  quarry,  and  has  remembered  how 
that,  when  he  has  been  breaking  it  up,  in  order, 
perhaps,  to  excavate  a  partially  hidden  fossil,  it 
has  readily  split  up  in  thin  flakes  or  layers  of 
shaly  substance.  This  exhibits,  on  a  small  scale, 
the  chief  peculiarity  of  the  coal  shales. 

The  formation  of  shales  will  now  demand  our 
attention.  When  a  river  is  carrying  down  with  it 
a  quantity  of  rnu'd  or  clay,  it  is  transported  as  a 
fine,  dusty  silt,  and  when  present  in  quantities, 
gives  the  muddy  tint  to  the  water  which  is  so  no- 
ticeable. We  can  very  well  see  how  that  silt  will 
be  carried  down  in  greater  quantities  than  sand, 
since  nearly  all  rivers  in  some  part  of  their 
course  will  _travel  through  a  clayey  district,  and 
finely  divided  clay,  being  of  a  very  light  nature, 
will  be  carried  forward  whenever  a  river  passes 


GENERAL  VIEW   OF   COAL-BEARING   STRATA.     43 

over  such  a  district.  And  a  very  slight  current 
being  sufficient  to  carry  it  in  a  state  of  suspen- 
sion, it  follows  that  it  will  have  little  opportunity 
of  falling  to  the  bottom,  until,  by  some  means  or 
other,  the  current,  which  is  the  means  of  its  con- 
veyance, becomes  stopped  or  hindered  consider- 
ably in  its  flow. 

When  the  river  enters  a  large  body  of  water, 
such  as  the  ocean  or  a  lake,  in  losing  its  individ- 
uality, it  loses  also  the  velocity  of  its  current, 
and  the  silt  tends  to  sink  down  to  the  bottom. 
But  being  less^eavy  than  the  sand,  about  which 
we  have  previously  spoken,  it  does  not  sink  all  at 
once,  but  partly  with  the  impetus  it  has  gained, 
and  partly  on  account  of  the  very  slight  velocity 
which  the  current  still  retains,  even  after  having 
entered  the  sea,  it  will  be  carried  out  some  dis- 
tance, and  will  the  more  gradually  sink  to  the 
bottom.  The  deeper  the  water  in  which  it  falls 
the  greater  the  possibility  of  its  drifting  farther 
still,  since  in  sinking,  it  would  fall,  not  vertically, 
but  rather  as  the  drops  of  rain  in  a  shower  when 
being  driven  before  a  gale  of  wind.  Thus  we 
should  notice  that  clays  and  shales  would  exhibit 
a  regularity  and  uniformity  of  deposition  over  a 
wide  area.  Currents  and  tides  in  the  sea  or  lake 
would  tend  still  further  to  retard  deposition, 
whilst  any  stoppages  in  the  supply  of  silt  which 
took  place  would  give  the  former  layer  time  to 
consolidate  and  harden,  and  this  would  assist  in 
giving  it  that  bedded  structure  which  is  so  no- 
ticeable in  the  shales,  and  which  causes  it  to 
split  up  into  fine  laminae.  This  uniformity  of 
structure  in  the  shales  over  wide  areas  is  a  well- 
ascertained  characteristic  of  the  coal-shales,  and 
we  may  therefore  regard  the  method  of  their 


44  THE   STORY  OF  A   PIECE   OF   COAL. 

deposition  as  given  here  with  a  degree  of  cer- 
tainty. 

There  is  a  class  of  deposit  found  among  the 
coal-beds,  which  is  known  as  the  "  undetelay," 
and  this  is  the  most  regular  of  all  as  to  the  posi- 
tion in  which  it  is  found.  The  underclays  are 
found  beneath  every  bed  of  coal.  u  Warrant," 
"  spavin,"  and  "  gannister  "  are  local  names  which 
are  applied  to  it  in  England,  the  last  term  being 
used  when  the  clay  contains  such  a  large  propor- 
tion of  silicious  matter  as  to  become  almost  like 
a  hard  flinty  rock.  Sometimes,  however,  it  is  a 
soft  clay,  at  others  it  is  mixed  with  sand,  but 
whatever  the  composition  of  the  underclays  may 
be,  they  always  agree  in  being  unstratified.  They 
also  agree  in  this  respect  that  the  peculiar  fossils 
known  as  stigmarm  abound  in  them,  and  in  some 
cases  to  such  an  extent  that  the  clay  is  one  thickly 
matted  mass  of  the  filamentous  rootlets  of  these 
fossils.  We  have  seen  how  these  gradually  came 
to  be  recognised  as  the  roots  of  trees  which  grew 
in  this  age,  and  whose  remains  have  subsequently 
become  metamorphosed  into  coal,  and  it  is  but 
one  step  farther  to  come  to  the  conclusion  that 
these  underclays  are  the  ancient  soils  in  which 
the  plants  grew. 

No  sketch  of  the  various  beds  which  go  to 
form  the  coal-measures  would  be  complete  which 
did  not  take  into  account  the  enormous  beds  of 
mountain  limestone  which  form  the  basis  of  the 
whole  system,  and  which  in  thinner  bands  are 
intercalated  amongst  the  upper  portion  of  the 
system,  or  the  true  coal-measures. 

Now,  limestones  are  not  formed  in  the  same 
way  in  which  we  have  seen  that  sandstones  and 
shales  are  formed.  The  last  two  mentioned  owe 


GENERAL   VIEW   OF   COAL-BEARING  STRATA.     45 

their  origin    to  their   deposition   as   sediment   in 
seas,  estuaries,  or  lakes,  but  the  masses  of  lime- 
stone which  are  found  in  the  various  geological 
formations  owe  their  origin   to 
causes  other  than   that  of  sedi- 
mentary deposition. 

In  carboniferous  times  there 
lived  numberless  creatures  which 
we  know  nowadays  as  encrinites. 
These,  when  growing,  were  fixed 
to  the  bed  of  the  ocean,  and  ex- 
tended upward  in  the  shape  of 
pliant  stems  composed  of  lime- 
stone joints  or  plates;  the  .^^  stem  of 
each  encrinite  then  ex-  ,$P^  panded 
at  the  top  in  the  shape  &<i$r^  °^  a  £or~ 
geous  and  graceful  star-  ^yp^  fish,  pos- 
sessed of 
numberless 
and  lengthy  arms. 
These  encrinites 
grew  in  such  pro- 
fusion that  after 
death,  when  the 
plates  of  which  their  stems  consisted,  became 
loosened  and  scattered  over  the  bed  of  the  sea, 
they  accumulated  and  formed  solid  beds  of  lime- 
stone. Besides  the  encrinites,  there  were  of  course 
other  creatures  which  were  able  to  create  the  hard 
parts  of  their  structures  by  withdrawing  lime 
from  the  sea,  such  as  foraminifera,  shell-fish,  and 
especially  corals,  so  that  all  these  assisted  after 
death  in  the  accumulation  of  beds  of  limestone 
where  they  had  grown  and  lived. 

There  is  one    peculiarity  in  connection  with 
the  habitats  of  the  encrinites  and   corals  which 


FIG.  20. — Encrinite. 


46 


THE   STORY   OF   A   PIECE   OF   COAL. 


goes  some  distance  in  supplying  us  with  a  useful 
clue  as  to  the  conditions  under  which  this  portion 
of  the  carboniferous  formation  was  formed. 
These  creatures  find  it  a  difficult  matter,  as  a 
rule,  to  live  and  secrete  their  calcareous  skeleton 
in  any  water  but  that  which  is  clear,  and  free 
from  muddy  or  sandy  sediment.  They  are  there- 
fore not  found, 
generally  speak- 
ing, where  the  oth- 
er deposits  which 
we  have  consid- 
ered, are  forming, 
and,  as  these  are 
always  found  near 
the  coasts,  it  fol- 
lows that  the  habi- 
tats of  the  crea- 
tures referred  to 
FIG.  21.— Encrinital  limestone.  must  be  far  out  at 

sea  where  no  mud- 
dy sediments,  borne  by  rivers,  can  reach  them. 
We  can  therefore  safely  come  to  the  conclusion 
that  the  large  masses  of  encrinital  limestone, 
which  attain  such  an  enormous  thickness  in  some 
places,  especially  in  Ireland,  have  been  formed  far 
away  from  the  land  of  the  period  ;  we  can  at  the 
same  time  draw  the  conclusion  that  if  we  find  the 
encrinites  broken  and  snapped  asunder,  and  the 
limestone  deposits  becoming  impure  through  be- 
ing mingled  with  a  proportion  of  clayey  or  sandy 
deposits,  that  we  are  approaching '  a  coast-line 
where  perhaps  a  river  opened  out,  and  where  it 
destroyed  the  growth  of  encrinites,  mixing  with 
their  dead  remains  the  sedimentary  debris  of  the 
land. 


GENERAL  VIEW   OF   COAL-BEARING  STRATA.     47 

We  have  lightly  glanced  at  the  circumstances 
attending  the  deposition  of  each  of  the  principal 
rocks  which  form  the  beds  amongst  which  coal  is 
found,  and  have  now  to  deal  with  the  formation 
of  the  coal  itself.  We  have  already  considered 
the  various  kinds  of  plants  and  trees  which  have 


FIG.   22. — Encrinites  :  various.     Mountain  limestone. 

been  discovered  as  contributing  their  remains  to 
the  formation  of  coal,  and  have  now  to  attempt 
an  explanation  of  how  it  came  to  be  formed  in  so 
regular  a  manner  over  so  wide  an  area. 

Few  countries  are  entirely  without  coal.  The 
United  States  has  by  far  the  largest  fields,  amount- 
ing to  about  190,000  square  miles.  There  are 
something  like  12,000  square  miles  in  the  British 
Isles,  and  deposits  of  considerable  extent  are 
found  on  the  continent  of  Europe,  in  Asia, 
Australia,  and  South  America.  And  yet,  spread 
over  them,  we  find  a  series  of  beds  of  coal  which 


V 


48  THE   STORY   OF  A   PIECE   OF  COAL. 

in  many  cases  extend  throughout  the  whole  area 
with  apparent  regularity.  If  we  take  it,  as  there 
seems  every  reason  to  believe  was  the  case,  that 
almost  all  these  coal-fields  were  not  only  being 
formed  at  the  same  time,  but  were  in  most  in- 
stances in  continuation  with  one  another,  this 
regularity  of  deposition  of  comparatively  narrow 
beds  of  coal,  appears  all  the  more  remarkable. 

The  question  at  once  suggests  itself,  Which  of 
two  things  is  probable  ?  Are  we  to  believe  that 
all  this  vegetable  matter  was  brought  down  by 
some  mighty  river  and  deposited  in  its  delta,  or 
that  the  coal-plants  grew  just  where  we  now  find 
the  coal  ? 

Formerly  it  was  supposed  that  coal  was 
formed  out  of  dead  leaves  and  trees,  the  refuse  of 
the  vegetation  of  the  land,  which  had  been  car- 
ried down  by  rivers  into  the  sea  and  deposited  at 
their  mouths,  in  the  same  way  that  sand  and  mud, 
as  we  have  seen,  are  swept  down  and  deposited. 
If  this  were  so,  the  extent  of  the  deposits  would 
require  a  river  with  an  enormous  embouchure, 
and  we  should  be  scarcely  warranted  in  believing 
that  such  peaceful  conditions  would  there  prevail 
as  to  allow  of  the  layers  of  coal  to  be  laid  down 
with  so  little  disturbance  and  with  such-regularity 
over  these  wide  areas.  But  the  great  objection 
to  this  theory  is,  that  not  only  do  the  remains 
still  retain  their  perfection  of  structure,  but  they 
are  comparatively  pure — /.  e.,  unmixed  with  sedi- 
mentary depositions  of  clay  or  sand.  Now,  rivers 
would  not  bring  down  the  dead  vegetation  alone ; 
their  usual  burden  of  sediment  would  also  be  de- 
posited at  their  mouths,  and  thus  dead  plants, 
sand,  and  clay  would  be  mixed  up  together  in 
one  black  shaly  or  sandy  mass,  a  mixture  which 


GENERAL   VIEW  OF  COAL-BEARING  STRATA.     49 

would  be  useless  for  purposes  of  combustion. 
The  only  theory  which  explained  all  the  recog- 
nised phenomena  of  the  coal-measures  was  that 
the  plants  forming  the  coal  actually  grew  where! 
the  coal  was  formed,  and  where,  indeed,  we  now\ 
find  it.  When  the  plants  and  trees  died,  their  re-  \ 
mains  fell  to  the  ground  of  the  forest,  and  these 
soon  turned  to  a  black,  pasty,  vegetable  mass, 
the  layer  thus  formed  being  regularly  increased 
year  by  year  by  the  continual  accumulation  of 
fresh  carbonaceous  matter.  By  this -means  a  bed 
would  be  formed  with  regularity  over  a  wide 
area;  the  coal  would  be  almost  free  from  an  ad- 
mixture of  sandy  or  clayey  sediment,  and  prob- 
ably the  rate  of  formation  would  be  no  more 
rapid  in  one  part  of  the  forest  than  another. 
Thus  there  would  be  everywhere  uniformity  of 
thickness.  The  warm  and  humid  atmosphere, 
which  it  is  probable  then  existed,  would  not 
only  have  tended  towards  the  production  of 
an  abnormal  vegetation,  but  would  have  assisted 
in  the  decaying  and  disintegrating  processes 
which  went  on  amongst  the  shed  leaves  and 
trees. 

When  at  last  it  was  announced  as  a  patent 
fact  that  every  bed  of  coal  possessed  its  under- 
day,  and  that  trees  had  been  discovered  actually 
standing  upon  their  own  roots  in  the  clay,  there 
was  no  room  at  all  for  doubt  that  the  correct 
theory  had  been  hit  upon — viz.,  that  coal  is  now 
found  just  where  the  trees  composing  it  had 
grown  in  the  past. 

But  we   have    more    than    one   coal-seam   to 

account  for.     We  have  to  explain  the  -existence 

of  several  layers  of  coal  which  have  been  formed 

over  one  another  on  the  same  spot  at  successive 

4 


50  THE   STORY  OF  A   PIECE   OF   COAL. 

periods,  divided  by  other  periods  when  shale  and 
sandstones  only  have  been  formed. 

A  careful  estimate  of  the  Lancashire  coal-field 
has  been  made  by  Professor  Hull  for  the  British 
Geological  Survey.  Of  the  7000  feet  of  carbonif- 
erous strata  here  found,  spread  out  over  an  area 
of  217  square  miles,  there  are  on  the  average 
eighteen  seams  of  coal. 

This  is  only  an  instance  of  what  is  to  be  found 
elsewhere.  Eighteen  coal-seams  !  what  does  this 
mean  ?  It  means  that,  during  carboniferous  times, 
on  no  less  than  eighteen  occasions,  separate  and 
distinct  forests  have  grown  on  this  self-same  spot, 
and  that  between  each  of  these  occasions  changes 
have  taken  place  which  have  brought  it  beneath 
the  waters  of  the  ocean,  where  the  sandstones 
and  shales  have  been  formed  which  divide  the 
coal-seams  from  each  other.  We  are  met  here 
by  a  wonderful  demonstration  of  the  instability 
of  the  surface  of  the  earth,  and  we  have  to  do 
our  best  to  show  how  the  changes  of  level  have 
been  brought  about,  which  have  allowed  of  this 
game  of  geological  see-saw  to  take  place  between 
sea  and  land.  Changes  of  level !  Many  a  hard 
geological  nut  has  only  been  overcome  by  the 
application  of  the  principle  of  changes  of  level 
in  the  surface  of  the  earth,  and  in  this  we  shall 
find  a  sure  explanation  of  the  phenomena  of  the 
coal-measures. 

Great  changes  of  the  level  of  the  land  are 
undoubtedly  taking  place  even  now  on  the 
earth's  surface,  and  in  assuming  that  similar 
changes  took  place  in  carboniferous  times,  we 
shall  not  be  assuming  the  former  existence  of 
an  agent  with  which  we  are  now  unfamiliar. 
And  when  we  consider  the  thicknesses  of  sand- 


GENERAL  VIEW  OF  COAL-BEARING  STRATA.     51 

stone  and  shale  which  intervene  beneath  the 
coal-seams,  we  can  realise  to  a  certain  extent 
the  vast  lapses  of  years  which  must  have  taken 
place  between  the  existence  of  each  forest ;  so 
that  although  now  an  individual  passing  up  a 
coal-mine  shaft  may  rapidly  pass  through  the 
remains  of  one  forest  after  another,  the  rise  of 
the  strata  above  each  forest-bed  then  was  tre- 
mendously slow,  and  the  period  between  the 
growth  of  each  forest  must  represent  the  passing 
away  of  countless  ages.  Perhaps  it  would  not 
be  too  much  to  say  that  the  strata  between 
some  of  the  coal-seams  would  represent  a  period 
not  less  than  that  between  the  formation  of  the 
few  tertiary  coals  with  which  we  are  acquainted, 
and  a  time  which  is  still  to  us  in  the  far-away 
future. 

The  actual  seams  of  coal  themselves  will  not 
yield  much  information,  from  which  it  will  be 
possible  to  judge  of  the  contour  of  the  land- 
masses  of  this  ancient  period.  Of  one  thing 
we  are  sure,  namely,  that  at  the  time  each  sean\ 
was  formed,  the  spot  where  it  accumulated  was > 
dry  land.  If,  therefore,  the  seams  which  appear 
one  above  the  other  coincide  fairly  well  as  to 
their  superficial  extent,  we  can  conclude  that 
each  time  the  land  was  raised  above  the  sea 
and  the  forest  again  grew,  the  contour  of  the 
land  was  very  similar.  The  conclusion  will  be 
very  useful  to  go  upon,  since  whatever  decision 
may  be  come  to  as  an  explanation  of  one  suc- 
cessive land-period  and  sea-period  on  the  same 
spot,  will  be  applicable  to  the  eighteen  or  more 
periods  necessary  for  the  completion  of  some  of 
the  coal-fields. 

We  will  therefore  look  at  one  of  the  sandstone 


52  THE   STORY   OF  A   PIECE   OF   COAL. 

masses  which  occur  between  the  coal-seams,  and 
learn  what  lessons  these  have  to  teach  us.  In 
considering  the  formation  of  strata  of  sand  in  the 
seas  around  our  river-mouths,  it  was  seen  that, 
owing  to  the  greater  weight  of  the  particles  of 
the  sand  over  those  of  clay,  the  former  the 
more  readily  sank  to  the  bottom,  and  formed 
banks  not  very  far  away  from  the  land.  It  was 
seen,  too,  that  each  successive  deposition  of  sand 
formed  a  wedge-shaped  layer,  with  the  point  of 
the  wedge  pointing  away  from  the  source  of 
origin  of  the  sediment,  and  therefore  of  the  cur- 
rent which  conveyed  the  sediment.  Therefore, 
if  in  the  coal-measure  sandstones  the  layers  were 
found  with  their  wedges  all  pointing  in  one  di- 
rection, we  should  be  able  to  judge  that  the 
currents  were  all  from  one  -direction,  and  that, 
therefore,  they  were  formed  by  a  single  river. 
But  this  is  just  what  we  do  not  find,  for  instead 
of  it  the  direction  of  the  wedge-shaped  strata 
varies  in  almost  every  layer,  and  the  current- 
bedding  has  been  brought  about  by  currents 
travelling  in  every  direction.  Such  diverse 
current-bedding  could  only  result  from  the  fact 
that  the  spot  where  the  sand  was  laid  down  was 
subject  to  currents  from  every  direction,  and 
the  inference  is  that  it  was  well  within  the 
sphere  of  influence  of  numerous  streams  and 
rivers,  which  flowed  from  every  direction.  The 
only  condition  of  things  which  would  explain 
this  is  that  the  sandstone  was  originally  formed 
in  a  closed  sea  or  large  lake,  into  which  numer- 
ous rivers  flowing  from  every  direction  poured 
their  contents. 

Now,  in  the  sandstones,  the  remains  of  numer- 
ous plants  have  been  found,  but  they  do  not  pre- 


GENERAL  VIEW  OF  COAL-BEARING  STRATA.  53 

sent  the  perfect  appearance  that  they  do  when 
found  in  the  shales;  in  fact  they  appear  to  have 
suffered  a  certain  amount  of  damage  through 
having  drifted  some  distance.  This,  together 
with  the  fact  that  sandstones  are  not  formed 
far  out  at  sea,  justify  the  safe  conclusion  that 
*the  land  could  not  have  been  far  off.  Wherever 
'the  current-bedding  shows  itself  in  this  manner 
e  may  be  sure  we  are  examining  a  spot  from 
which  the  land  in  every  direction  could  not  have 
been  at  a  very  great  distance,  and  .also  that, 
since  the  heavy  materials  of  which  sandstone  is 
composed  could  only  be  transported  by  being 
impelled  along  by  currents  at  the  bed  of  the  sea, 
and  that  in  deep  water  such  currents  could  not 
exist,  therefore  we  may  safely  decide  that  the 
sea  into  which  the  rivers  fell  was  a  comparatively 
shallow  one. 

Although  the  present  coal-fields  of  England 
are  divided  from  one  another  by  patches  of  other 
beds,  it  is  probable  that  some  of  them  were  for- 
merly connected  with  others,  and  a  very  wide 
sheet  of  coal  on  each  occasion  was  laid  down. 
The  question  arises  as  to  what  was  the  extent 
of  the  inland  sea  or  lake,  and  did  it  include  the 
area  covered  by  the  coal  basins  of  Scotland  and 
Ireland,  of  France  and  Belgium  ?  And  if  these, 
why  not  those  of  America  and  other  parts  ? 
The  deposition  of  the  coal,  according  to  the  the- 
ory here  advanced,  may  as  well  have  been  brought 
about  in  a  series  of  large  inland  seas  and  lakes, 
as  by  one  large  comprehensive  sea,  and  probably 
the  former  is  the  more  satisfactory  explanation 
of  the  two.  But  the  astonishing  part  of  it  is 
that  the  changes  in  the  level  o*f  the  land  must 
have  been  taking  place  simultaneously  over  these 


54  THE   STORY   OF   A   PIECE   OF   COAL. 

large  areas,  although,  of  course,  while  one  quar- 
ter may  have  been  depressed  beneath  the  sea, 
another  may  have  been  raised  above  it. 

In  connection  with  the  question  of  the  con- 
tour of  the  land  during  the  existence  of  the  large 
lakes  or  inland  seas,  Professor  Hull  has  prepared, 
in  his  series  of  maps  illustrative  of  the  Palseo- 
Geography  of  the  British  Islands,  a  map  show- 
ing on  incontestible  grounds  the  existence  during 
the  coal-ages  of  a  great  central  barrier  or  ridge 
of  high  land  stretching  across  from  Anglesea, 
south  of  Flint,  Staffordshire,  and  Shropshire  coal- 
fields, to  the  eastern  coast  of  Norfolk.  He  re- 
gards the  British  coal-measures  as  having  been 
laid  down  in  two,  or  at  most  three,  areas  of  dep- 
osition— one  south  of  this  ridge,  the  remainder 
to  the  north  of  it.  In  regard  to  the  extent  of 
the  former  deposits  of  coal  in  Ireland,  there  is 
every  probability  that  the  sister  island  was  just 
as  favourably  treated  in  this  respect  as  Great 
Britain.  Most  unfortunately,  Ireland  has  since 
suffered  extreme  denudation,  notably  from  the 
great  convulsions  of  nature  at  the  close  of  the 
very  period  of  their  deposition,  as  well  as  in  more 
recent  times,  resulting  in  the  removal  of  nearly 
all  the  valuable  upper  carboniferous  beds,  and 
leaving  only  the  few  unimportant  coal-beds  to 
which  reference  has  been  made. 

We  are  unable  to  believe  in  the  continuity  of 
the  English  and  American  coal-beds,  for  the 
great  source  of  sediment  in  those  times  was  a 
continent  situated  on  the  site  of  the  Atlantic 
Ocean,  and  it  is  owing  to  this  extensive  continent 
that  the  forms  of  flora  found  in  the  coal-beds  in 
each  country  bear  so  close  a  resemblance  to  one 
another,  and  also  that  the  encrinital  limestone 


GENERAL   VIEW   OF   COAL-BEARING   STRATA.     55 


which  was  formed  in  the  purer  depths  of  the 
ocean  on  the  east,  became  mixed  with  silt,  and 
formed  masses  of  shaly  impure 
limestone  in  the  south-western 
parts  of  Ireland. 

It  must  be  noted  that,  al- 
though we  may  attribute  to  up- 
heaval from  beneath  the  fact  that 
the  bed  of  the  sea  became  tem- 
porarily raised  at  each  period  in- 
to dry  land,  the  deposits  of  sand 
or  shale  would  at  the  same  time 
be  tending  to  shallow  the  bed, 
and  this  alone  would  assist  the 
process  of  upheaval  by  bringing 
the  land  at  least  very  near  to  the 
surface  of  the  water. 

Each  upheaval,  however, 
could  have  been  but  a  temporary  arrest  of 
great  movement  of  crust  subsidence  which  was 
going  on  throughout  the  coal-period,  so  that,  at 
its  close,  when  the  last  coal-forest  grew  upon  the 
surface  of  the  land,  there  had  disappeared,  in  the 
case  of  South  Wales,  a  thickness  of  11,000  feet  of 
material. 

Of  the  many  remarkable  things  in  connection 
with  coal-beds,  not  the  least  is  the  state  of  purity 
in  which  coal  is  found.  On  the  floor  of  each 
forest  there  would  be  many  a  streamlet  or  even 
small  river  which  would  wend  its  way  to  meet 
the  not  very  distant  sea,  and  it  is  surprising  at 
first  that  so  little  sediment  found  its  way  into  the 
coal  itself.  But  this  was  cleverly  explained  by 
Sir  Charles  Lyell,  who  noticed,  on  one  of  his 
visits  to  America,  that  the  water  of  the  Missis- 
sippi, around  the  rank  growths  of  cypress  which 


FIG.  23. — Cyatho- 
phyllum.  Coral  in 
encrinital  limestone. 


the 


56  THE  STORY  OF  A   PIECE  OF  COAL. 

form  the  "cypress  swamps"  at  the  mouths  of 
that  river,  was  highly  charged  with  sediment,  but 
that,  having  passed  through  the  close  under- 
growth of  the  swamps  it  issued  in  almost  a  pure 
state,  the  sediment  which  it  bore  having  been 
filtered  out  of  it  and  precipitated.  This  very  sat- 
isfactorily explained  how  in  some  places  carbon- 
aceous matter  might  be  deposited  in  a  perfectly 
pure  state,  whilst  in  others,  where  sandstone  or 
shale  was  actually  forming,  it  might  be  impreg- 
nated by  coaly  matter  in  such  a  way  as  to  cause 
it  to  be  stained  black.  In  times  of  flood  sediment 
would  be  brought  in,  even  where  pure  coal  had 
been  forming,  and  then  we  should  have  a  thin 
"parting"  of  sandstone  or  shale,  which  was 
formed  when  the  flood  was  at  its  height.  Or  a 
slight  sinking  of  the  land  might  occur,  in  which 
case  also  the  formation  of  coal  would  temporarily 
cease,  and  a  parting  of  foreign  matter  would  be 
formed,  which,  on  further  upheaval  taking  place, 
would  again  give  way  to  another  forest  growth. 
Some  of  the  thicker  beds  have  been  found  pre- 
senting this  aspect,  such  as  the  South  Stafford- 
shire ten-yard  coal,  which  in  some  parts  splits  up 
into  a  dozen  or  so  smaller  beds,  with  partings  of 
sediment  between  them. 

In  the  face  of  the  stupendous  movements 
which  must  have  happened  in  order  to  bring 
about  the  successive  growth  of  forests  one  above 
another  on  the  same  spot,  the  question  at  once 
arises  as  to  how  these  movements  of  the  solid 
earth  came  about,  and  what  was  the  cause  which 
operated  in  such  a  manner.  We  can  only  judge 
that,  in  some  way  or  other,  heat,  or  the  with- 
drawal of  heat,  has  been  the  prime  motive  power. 
We  can  perceive,  from  what  is  now  going  on  in 


GENERAL   VIEW  OF   COAL-BEARING   STRATA.     57 

some  parts  of  the  earth,  how  great  an  influence  it 
has  had  in  shaping  the  land,  for  volcanoes  owe 
their  activity  to  the  hidden  heat  in  the  earlh's 
interior,  and  afford  us  an  idea  of  the  power  of 
which  heat  is  capable  in  the  matter  of  building 
up  and  destroying  continents.  No  less  certain  is 
it  that  heat  is  the  prime  factor  in  those  more 
gradual  vertical  movements  of  the  land  to  which 
we  have  referred  elsewhere,  but  in  regard  to  the 
exact  manner  in  which  it  acts  we  are  very  much 
in  the  dark.  Everybody  knows  that,  in  the  ma- 
jority of  instances,  material  substances  of  all 
kinds  expand  under  the  influence  of  heat,  and 
contract  when  the  source  of  heat  is  withdrawn. 
If  we  can  imagine  movements  in  the  quantity  of 
heat  contained  in  the  solid  crust,  the  explanation 
is  easy,  for  if  a  certain  tract  of  land  receive  an 
accession  of  heat  beneath  it,  it  is  certain  that  the 
principal  effect  will  be  an  elevation  of  the  land, 
consequent  on  the  expansion  of  its  materials,  with 
a  subsequent  depression  when  the  heat  beneath 
the  tract  in  question  becomes  gradually  lessened. 
Should  the  heat  be  retained  for  a  long  period,  the 
strata  would  be  so  uplifted  as  to  fo'rm  an  anti- 
clinal, or  saddle-back,  and  then,  should  subse- 
quent denudation  take  place,  more  ancient  strata 
would  be  brought  to  view.  Denudation  has  in 
fact  carried  away  much  of  the  upper  portion  of 
all  coal-bearing  strata,  whether  upheaved  or  hori- 
zontal, so  that  in  many  localities  as  in  northern 
Pennsylvania  the  coal  is  left  in  isolated  patches 
which  may  form  either  mountains  or  basins. 

How  the  heat-waves  act,  and  the  laws,  if  any, 

which  they  obey  in  their  subterranean  movements, 

I    we  are   unable  to   judge.      From   the  properties 

which  heat  possesses  we  know  that  its  presence 


58  THE   STORY   OF   A   PIECE   OF   COAL. 

or  absence  produces  marked  differences  in  the 
positions  of  the  strata  of  the  earth,  and  from 
observations  made  in  connection  with  the  closing 
of  some  volcanoes,  and  the  opening  up  of  fresh 
earth-vents,  we  have  gone  a  long  way  towards 
establishing  the  probability  that  there  are  even 
now  slow  and  ponderous  movements  taking  place 
in  the  heat  stored  in  the  earth's  crust,  whose 
effects  are  appreciably  communicated  to  the  out- 
side of  the  thin  rind  of  solid  earth  upon  which  we 
live.  ( 

Owing  to  the  great  igneous  and  volcanic  ac-\ 
tivity  at  the  close  of  the  deposition  of  the  car-  J 
boniferous  system  of  strata,  the  coal-measures  / 
exhibit  what  are  known  as  faults  in  abundance*: 
The  mountain  limestone,  where  it  outcrops  at  the 
surface,  is  observed  to  be  much  jointed,  so  much 
so  that  the  work  of  quarrying  the  limestone  is 
greatly  assisted  by  the  jointed  structure  of  the 
rock.  Faults  differ  from  joints  in  that,  whilst 
the  strata  in  the  latter  are  still  in  relative  posi- 
tion on  each  side  of  the  joint,  they  have  in  the 
former  slipped  out  of  place.  In  such  a  case  the 
continuation  of  a  stratum  on  the  opposite  side  of 
a  fault  will  be  found  to  be  depressed,  perhaps  a 
thousand  feet  or  more.  It  will  be  seen  at  once 
how  that,  in  sinking  a  new  shaft  into  a  coal-seam, 
the  possibility  of  an  unknown  fault  has  to  be 
brought  into  consideration,  since  the  position  of 
the  seam  may  prove  to  have  been  depressed  to 
such  an  extent  as  to  cause  it  to  be  beyond  work- 
able depth.  Many  seams,  on  the  other  hand, 
which  would  have  remained  altogether  out  of 
reach  of  mining  operations,  have  been  brought 
within  workable  depth  by  a  series  of  step-faults, 
this  being  a  term  applied  to  a  series  of  parallel 


GENERAL   VIEW   OF   COAL-BEARING   STRATA.     59 

faults,  in  none  of  which  the  amount  of  down- 
throw is  great. 

The  amount  of  the  down-throw,  or  the  slip- 
ping-down  of  the  beds,  is  measured,  vertically, 
from  the  point  of  disappearance  of  a  layer  to  an 
imaginary  continuation  of  the  same  layer  from 
where  it  again  appears  beyond  the  fault.  The 
plane  of  a  fault  is  usually  more  or  less  inclined, 
the  amount  of  the  inclination  being  known  as  the 
hajc  of  the  fault,  and  it  is  a  remarkable  charac- 
teristic of  faults  that,  as  a  general  rule,  they  hade 
to  the  down-throw.  This  will  be  more  clearly  un- 
derstood when  it  is  explained  that,  by  its  action, 
a  seam  of  coal,  which  is  subject  to  numerous 
faults,  can  never  be  pierced  more  than  once  by 
one  and  the  same  boring.  In  mountainous  dis- 
tricts, however,  there  are  occasions  when  the 
hade  is  to  the  up-throw,  and  this  kind  of  fault  is 
known  as  an  inverted  fault. 

Lines  of  faults  extend  sometimes  for  hundreds 
of  miles.  The  great  Pennine  Fault  of  England 
is  130  miles  long,  and  others  extend  for  much 
greater  distances.  The  surfaces  on  both  sides  of 
a  fault  are  often  smooth  and  highly  polished  by 
the  movement  which  has  taken  place  in  the 
strata.  They  then  show  the  phenomenon  known 
as  slicken-sides.  Many  faults  have  become  filled 
with  crystalline  minerals  in  the  form  of  veins  of 
ore,  deposited  by  infiltrating  waters  percolating 
through  the  natural  fissures. 

In  considering  the  formation  and  structure  of 
the  better-known  coal-bearing  beds  of  the  car- 
boniferous age,  we  must  not  lose  sight  of  the  fact 
that  important  beds  of  coal  also  occur  in  strata 
of  much  more  recent  date.  There  are  important 
coal-beds  in  India  of  Permian  age.  There  are 


60  THE   STORY   OF  A   PIECE   OF   COAL, 

coal-beds  of  Liassic  age  in  South  Hungary  and 
in  Texas,  and  of  Jurassic  age  in  Virginia,  as  well 
as  at  Brora  in  Scotland  ;  there  are  large  deposits 
of  Cretaceous  age  in  western  North  America; 
Cretaceous  coal  is  also  found  in  Moravia  and 
Miocene  Tertiary  in  Hungary. 

Again,  older  than  the  true  carboniferous  age, 
are  the  Silurian  anthracites  of  Co.  Cavan,  and 
certain  Norwegian  coals,  whilst  in  New  South 
Wales  we  are  confronted  with  an  assemblage  of 
coal-bearing  strata  which  extend  apparently  from 
the  Devonian  into  Mesozoic  times. 

Still,  the  age  we  have  considered  more  closely 
has  an  unrivalled  right  to  the  title,  coal  appear- 
ing there  not  merely  as  an  occasional  bed,  but  as 
a  marked  characteristic  of  the  formation. 

The  types  of  animal  life  which  are  found  in 
this  formation  are  varied,  and  although  naturally 
enough  they  do  not  excel  in  number,  there  are 
yet  sufficient  varieties  to  show  probabilities  of 
the  existence  of  many  with  which  we  are  un- 
familiar. The  highest  forms  yet  found,  show  an 
advance  as  compared  with  those  from  earlier  for- 
mations, and  exhibit  amphibian  characteristics, 
intermediate  between  the  two  great  classes  of 
fishes  and  reptiles.  Numerous  specimens  proper 
to  the  extinct  order  of  labyrinthodontia  have  been 
arranged  into  at  least  a  score  of  genera,  these 
having  been  drawn  from  the  coal-measures  of 
Newcastle,  Edinburgh,  Kilkenny,  Saarbruck,  Ba- 
varia, Pennsylvania,  and  elsewhere.  The  Arche* 
gosaurus,  which  we  have  figured,  and  the  Anthra- 
cosaurus,  are  forms  which  appear  to  have  existed 
in  great  numbers  in  the  swamps  and  lakes  of  the 
age.  The  fish  of  the  period  belong  almost  en- 
tirely to  the  ancient  orders  of  the  ganoids  and 


GENERAL  VIEW  OF  COAL-BEARING  STRATA.  6 1 


placoids.     Of  the  ganoids,  the  great  megalichthys 

Hibberti  ranges  throughout  the  whole  of  the  sys- 

tem.   Wonderful  ac- 

cumulations of  fish 

remains    are    found 

at  the  base  of   the 

system,  in  the  bone- 

bed    of    the   Bristol 

coal-field,  as  well  as 

in    a     similar     bed 

at  Armagh.      Many 

fishes    were    armed 

with  powerful  coni- 

cal    teeth,    but    the 

majority,     like     the 

existing  Port  Jack- 

son shark,  were  pos- 

sessed   of     massive 

palates,     suited     in 

some       cases       for 

crushing,      and     in 

others  for  cutting. 

In  the  mountain      FIG         ArcJke     aurta  minor. 

limestone  we  See,  Of  Coal-measures. 

course,  the  predom- 

inance of  marine  types,  encrinital  remains  form- 
ing the  greater  proportion  of  the  mass.  There  are 
occasional  plant  remains  which  bear  evidence  of 

having  drifted  for 
some  distance  from 
the  shore.  But 
next  to  the  encri- 
nites^  the  corals 
are  the  most  im- 


Crushing  palate  of  a  fish. 


P°rtant 

SIStent.       Corals  Ot 


62 


THE   STORY  OF  A   PIECE  OF  COAL. 


most  beautiful  forms  and  capable  of  giving  pol- 
ished marble-like  sections,  are  in  abundance. 
Polyzoa  are  well  represented,  of 
which  the  lace-coral  {fenestella) 
and  screw-coral  (archimedopora) 
are  instances.  Cephalopoda  are 
represented  by  the  orthoceras, 
sometimes  five  or  six  feet  long, 
and  goniatites,  the  forerunner  of 
the  familiar  ammonite.  Many 
species  of  brachiopods  and  la- 
mellibranchs  are  met  with.  Lin- 
gula,  most  persistent  through- 
out all  geological  time,  is  abun- 
dant in  the  coal-shales,  but  not 
in  the  limestones.*  Aviculopecten 
is  there  abundant  also.  In  the 
mountain  limestone  the  last  of 

FIG.  ^.-Orthoceras.   'he       trilobitCS      (Phillipsid)      IS 
Mountain  limestone,     found. 


We  have  evi- 
dence of  the  ex- 
istence in  the  for- 
ests of  a  variety 
of  centipede,  speci- 
mens having 
been  found  in  the 
erect  stump  of  a 
hollow  tree,  al- 
though the  fossil 
is  an  extremely 
rare  one.  The 
same  may  be  said 
of  the  only  two 
species  of  land- 


FIG.  27. — Fenestella  retipora. 
Mountain  limestone. 


GENERAL  VIEW  OF  COAL-BEARING  STRATA.      63 


snail  which  have  been  found  connected  with  the 
coal- forests,  viz.,  pupa  vetusta  and  zonites  priscus, 
both  discov- 
ered in  the 
cliffs  of  Nova 
Scotia.  These 
are  sufficient 

to  demon-      FIG.  2&.—Goniatites.     Mountain  limestone, 

strate  that  the 

fauna  of  the  period  had  already  reached  a  high 
stage  of  development.     In  the  estuaries  of  the 


FIG.  29. — Aviculopecten  papyraceus.     Coal-shale. 

day,  masses  of  a  species  of  freshwater  mussel 
(anthracosid]  were  in  existence,  and  these  have 
left  their  remains  in  the  shape  of  extensive  beds* 
of  shells.  They  are  familiar  to  the  English  miner 
as  mussel-binds,  and  are  as  noticeable  a  feature 


64  THE  STORY   OF  A   PIECE  OF  COAL. 

of  this  long-ago  period,  as  are  the  aggregations 
of  mussels  on  every  coast  at  the  present  day. 


CHAPTER   III. 

VARIOUS    FORMS    OF    COAL    AND    CARBON. 

IN  considering  the  various  forms  and  combi- 
nations into  which  coal  enters,  it  is  necessary  that 
we  should  obtain  a  clear  conception  of  what  the 
substance  called  k<  carbon  "  is,  and  its  nature  and 
properties  generally,  since  this  it  is  which  forms 
such  a  large  percentage  of  all  kinds  of  coal,  and 
which  indeed  forms  the  actual  basis  of  it.  In  the 
shape  of  coke,  of  course,  we  have  a  fairly  pure 
form  of  carbon,  and  this  being  produced,  as  we 
shall  see  presently,  by  the  driving  off  of  the  vola- 
tile or  vaporous  constituents  of  coal,  we  are  able 
to  perceive  by  the  residue  how  great  a  propor- 
tion of  coal  consists  of  carbon.  In  fact,  the  two 
have  almost  an  identical  meaning  in  the  popular 
mind,  and  the  fact  that  the  great  masses  of 
strata,  in  which  are  contained  our  principal  and 
most  valuable  seams  of  coal,  are  termed  "car- 
boniferous," from  the  Latin  carbo,  coal,  and  feroy 
I  bear,  tends  to  perpetuate  the  existence  of  the 
idea. 

There  is  always  a  certain,  though  slight,  quan- 
tity of  carbon  in  the  air,  and  this  remains  fairly 
constant  in  the  open  country.  Small  though  it 
may  be  in  proportion  to  the  quantity  of  pure  air 
in  which  it  it  found,  it  is  yet  sufficient  to  provide 
the  carbon  which  is  necessary  to  the  growth  of 
vegetable  life.  Just  as  some  of  the  animals 


VARIOUS  FORMS  OF  COAL  AND  CARBON.   65 

known  popularly  as  'the  zoophytes,  which  are 
attached  during  life  to  rocks  beneath  the  sea, 
are  fed  by  means  of  currents  of  water  which 
bring  their  food  to  them,  so  the  leaves,  which 
inhale  carbon-food  during  the  day  through  their 
under-surfaces,  are  provided  with  it  by  means  of 
the  currents  of  air  which  are  always  circulating 
around  them;  and  while  the  fuel  is  being  taken 
in  beneath,  the  heat  and  light  are  being  received 
from  above,  and  the  sun  supplies  the  motive 
power  to  digestion. 

It  is  assumed  that  it  is  within  the  knowledge 
of  all  that,  for  the  origin  of  the  various  seams 
and  beds  of  coaly  combinations  which  exist  in  the 
earth's  crust,  we  must  look  to  the  vegetable  world. 
If,  however,  we  could  go  so  far  back  in  the  world's 
history  as  the  period  when  our  incandescent  orb 
had  only  just  severed  connection  with  a  gradu- 
ally diminishing  sun,  we  should  probably  find  the 
carbon  there,  but  locked  up  in  the  bonds  of 
chemical  affinities  with  other  elements,  and  exist- 
ing therewith  in  a  gaseous  condition.  But,  as 
the  solidifying  process  went  on  and  as  the  vege- 
table world  afterwards  made  its  appearance,  the 
carbon  became,  so  to  speak,  wrenched  from  its 
combinations,  and  being  absorbed  by  trees  and 
plants,  finally  became  deposited  amongst  the  ruins 
of  a  former  vegetable  world,  and  is  now  presented 
to  us  in  the  form  of  coal. 

We  are  able  to  trace  the  gradual  changes 
through  which  the  pasty  mass  of  decaying  vege- 
tation passed,  in  consequence  of  the  fact  that  we 
have  this  material  locked  up  in  various  stages  of 
carbonisation,  in  the  strata  beneath  our  feet. 
These  we  propose  to  deal  with  individually,  in  as 
unscientific  and  untechnical  a  manner  as  possible. 
5 


66  THE   STORY   OF  A   PIECE   OF  COAL. 

First  of  all,  when  a  mass  of  vegetable  matter 
commences  to  decay,  it  soon  loses  its  colour. 
There  is  no  more  noticeable  proof  of  this,  than 
that  when  vitality  is  withdrawn  from  the  leaves 
of  autumn,  they  at  once  commence  to  assume  a 
rusty  or  an  ashen  colour.  Let  the  leaves  but  fall 
to  the  ground,  and  be  exposed  to  the  early  frosts 
of  October,  the  damp  mists  and  rains  of  No- 
vember, and  the  rapid  change  of  colour  is  at 
once  apparent.  Trodden  under  foot  they  soon 
assume  a  dirty  blackish  hue,  and  even  when 
removed  they  leave  a  carbonaceous  trace  of 
themselves  behind  them,  where  they  had  rested. 
Another  proof  of  the  rapid  acquisition  of  their 
coaly  hue  is  noticeable  in  the  spring  of  the  year. 
When  the  trees  have  burst  forth  and  the  buds 
are  rapidly  opening,  the  cases  in  which  the  buds 
of  such  trees  as  the  horse-chestnut  have  been 
enclosed  will  be  found  cast  off,  and  strewing  the 
path  beneath.  Moistened  by  the  rains  and  the 
damp  night-mists,  and  trodden  under  foot,  these 
cases  assume  a  jet  black  hue,  and  are  to  all  appear- 
ance like  coal  in  the  very  first  stages  of  formation. 

But  of  course  coal  is  not  made  up  wholly  and 
only  of  leaves.  The  branches  of  trees,  twigs  of 
all  sizes,  and  sometimes  whole  trunks  of  trees 
are  found,  the  last  often  remaining  in  their  up- 
right position,  and  piercing  the  strata  which  have 
been  formed  above  them.  At  other  times  they 
lie  horizontally  on  the  bed  of  coal,  having  been 
thrown  down  previously  to  the  formation  of  the 
shale  or  sandstone,  which  now  rests  upon  them. 
They  are  often  petrified  into  solid  sandstone 
themselves,  whilst  leaving  a  rind  of  coal  where 
formerly  was  the  bark. '  Although  the  trunk  of 
a  tree  looks  so  very  different  to  the  leaves 


VARIOUS  FORMS  OF  COAL  AND  CARBON,   67 

which  it  bears  upon  its  branches,  it  is  only  natu- 
rally to  be  supposed  that,  as  they  are  both  built 
up  after  the  same  manner  from  the  juices  of  the 
earth  and  the  nourishment  in  the  atmosphere, 
they  would  have  a  similar  chemical  composi- 
tion. One  very  palpable  proof  of  the  carbonace- 
ous character  of  tree-trunks  suggests  itself.  Take 
in  your  hand  a  few  dead  twigs  or  sticks  from  which 
the  leaves  have  long  since  dropped  ;  pull  away 
the  dead  parts  of  the  ivy  which  has  been  creep- 
ing over  the  summer-house;  or  clasp  a  gnarlftd 
old  monster  of  the  forest  in  your  arms,  and  you 
will  quickly  find  your  hand  covered  with  a  black 
smut,  which  is  nothing  but  the  result  of  the  first 
stage  which  the  living  plant  has  made,  in  its  prog- 
ress towards  its  condition  as  dead  coal.  But 
an  easy,  though  rough,  chemical  proof  of  the 
constituents  of  wood,  can  be  made  by  placing  a 
few  pieces  of  wood  in  a  medium-sized  test-tube, 
and  holding  it  over  a  flame.  In  a  short  time  a 
certain  quantity  of  steam  will  be  driven  off,  next 
the  gaseous  constituents  of  wood,  and  finally 
nothing  will  be  left  but  a  few  pieces  of  black 
brittle  charcoal.  The  process  is  of  course  the 
same  in  a  fire-grate,  only  that  here  more  com- 
plete combustion  of  the  wood  takes  place  owing  ' 
to  its  being  immediately  exposed  to  the  action  of 
the  flames.  If  we  adopt  the  same  experiment 
with  some  pieces  of  coal,  the  action  is  similar,  only 
that  in  this  case  the  quantity  of  gases  given  off  is 
not  so  great,  coal  containing  a  greater  proportion 
of  carbon  than  wood,  owing  to  the  fact  that,  dur- 
ing its  long  burial  in  the  bowels  of  the  earth,  it 
has  been  acted  upon  in  such  a  way  as  to  lose  a 
great  part  of  its  volatile  constituents. 

From   processes,    therefore,   which  are  to    be 


68  THE   STORY   OF   A   PIECE   OF   COAL. 

seen  going  on  around  us,  it  is  easily  possible  to 
satisfy  ourselves  that  vegetation  will  in  the  long 
run  undergo  such  changes  as  will  result  in  the 
formation  of  coal. 

There  are  certain  parts  in  most  countries,  and 
particularly  in  Ireland,  where  masses  of  vegetation 
have  undergone  a  still  further  change  in  meta- 
morphism,  namely,  in  the  well-known  and  famous 
peat-bogs.  Ireland  is  par  excellence  the  land  of 
bogs,  some  three  millions  of  acres  being  said  to 
be  covered  by  them,  and  they  yield  an  almost 
inexhaustible  supply  of  peat.  One  of  the  peat- 
bogs near  the  Shannon  is  between  two  and  three 
miles  in  breadth  and  no  less  than  fifty  in  length, 
whilst  its  depth  varies  from  13  feet  to  as  much 
as  47  feet.  Peat-bogs  have  in  no  way  ceased  to  bq 
formed,  for  at  their  surfaces  the  peat-moss  grow$ 
afresh  every  year  ;  and  rushes,  horse-tails,  ancj 
reeds  of  all  descriptions  grow  and  thrive  each 
year  upon  the  ruins  of  their  ancestors.  The  for- 
mation of  such  accumulations  of  decaying  vege- 
tation would  only  be  possible  where  the  physical 
conditions  of  the  country  allowed  of  an  abundant 
rainfall,  and  depressions  in  the  surface  of  the 
land  to  retain  the  moisture.  Where  extensive 
"deforesting  operations  have  taken  place,  peat-bogs 
have  often  been  formed,  and  many  of  those  in 
existence  in  Europe  undoubtedly  owe  their  forma- 
tion to  that  destruction  of  forests  which  went  on 
under  the  sway  of  the  Romans.  Natural  drainage 
would  soon  be  obstructed  by  fallen  trees,  and  the 
formation  of  marsh-land  would  follow;  then  with 
the  growth  of  marsh-plants  and  their  successive 
annual  decay,  a  peaty  mass  would  collect,  which 
w'ould  quickly  grow  in  thickness  without  let  or 
hindrance. 


VARIOUS  FORMS  OF  COAL  AND  CARBON.   69 

In  considering  the  existence  of  inland  peat- 
bogs, we  must  not  lose  sight  of  the  fact  that  there 
are  subterranean  forest-beds  on  various  parts  of 
our  coasts,  which  also  rest  upon  their  own  beds 
of  peaty  matter,  and  very  possibly  when  in  the 
future  they  are  covered  up  by  marine  deposits, 
they  will  have  fairly  started  on  their  way  towards 
becoming  coal. 

Peat-bogs  do  not  wholly  consist  of  peat,  and 
nothing  else.  The  trunks  of  such  trees  as  the 
oak,  yew,  and  fir,  are  often  found  mingled  with 
the  remains  of  mosses  and  reeds,  and  these  often 
assume  a  decidedly  coaly  aspect.  From  the 
famous  Bog  of  Allen  in  Ireland,  pieces  of  oak, 
generally  known  as  "bog-oak,"  which  have  been 
buried  for  generations  in  peat,  have  been  ex- 
cavated. These  are  as  black  as  any  coal  can 
well  be,  and  are  sufficiently  hard  to  allow  of  their 
being  used  in  the  manufacture  of  brooches  and 
other  ornamental  objects.  Another  use  to  which 
peat  of  some  kinds  has  been  put  is  in  the  manu- 
facture of  yarn,  the  result  being  a  material  which 
is  said  to  resemble  brown  worsted.  On  digging 
a  ditch  to  drain  a  part  of  a  swamp  in  Maine,, 
in  which  peat  to  a  depth  of  twenty  feet  had  ac- 
cumulated, a  substance  similar  to  cannel  coal 
itself  was  found.  As  we  shall  see  presently, 
cannel  coal  is  one  of  the  earliest  stages  of  true 
coal,  and  the  discovery  proved  that  under  certain 
conditions  as  to  heat  and  pressure,  which  in  this 
case  happened  to'be  present,  the  materials  which 
form  peat  may  also  be  metamorphosed  into  true 
coal. 

Darwin,  in  his  well-known  "  Voyage  in  the 
Beagle"  gives  a  peculiarly  interesting  description 
of  the  condition  of  the  peat-beds  in  the  Chonos 


yo  THE   STORY  OF  A   PIECE   OF  COAL. 

Archipelago,  off  the  Chilian  coast;  and  of  their 
mode  of  formation.  "  In  these  islands,"  he  says, 
"  cryptogamic  plants  find  a  most  congenial 
climate,  and  within  the  forest  the  number  of 
species  and  great  abundance  of  mosses,  lichens, 
and  small  ferns,  is  quite  extraordinary.  In  Tierra 
del  Fuego  every  level  piece  of  land  is  invariably 
covered  by  a  thick  bed  of  peat.  In  the  Chonos 
Archipelago  where  the  nature  of  the  climate  more 
closely  approaches  that  of  Tierra  del  Fuego,  every 
patch  of  level  ground  is  covered  by  two  species 
of  plants  {Astelia  pumila  and  Donatia  megellanicci), 
which  by  their  joint  decay  compose  a  thick  bed 
of  elastic  peat. 

"  In  Tierra  del  Fuego,  above  the  region  of 
woodland,  the  former  of  these  eminently  sociable 
plants  is  the  chief  agent  in  the,  production  of  peat. 
Fresh  leaves  are  always  succeeding  one  to  the 
other  round  the  central  tap-root ;  the  lower  ones 
soon  decay,  and  in  tracing  a  root  downwards  in 
the  peat,  the  leaves,  yet  holding  their  places,  can 
be  observed  passing  through  every  stage  of  de- 
composition, till  the  whole  becomes  blended  in 
one  confused  mass.  The  Astelia  is  assisted  by  a 
few  other  plants, — here  and  there  a  small  creep- 
ing Myrtus  (M.  nummularia),  with  a  woody  stem 
like  our  cranberry  and  with  a  sweet  berry, — an 
Empetrum  (£.  rubrum\  like  our  heath, — a  rush 
(Juncus  grandiflorus),  are  nearly  the  only  ones 
that  grow  on  the  swampy  surface.  These  plants, 
though  possessing  a  very  close  general  resem- 
blance to  the  English  species  of  the  same  genera, 
are  different.  In  the  more  level  parts  of  the 
country  the  surface  of  the  peat  is  broken  up  into 
little  pools  of  water,  which  stand  at  different 
heights,  and  appear  as  if  artificially  excavated. 


VARIOUS  FORMS  OF  COAL  AND  CARBON.   71 


Small  streams  of  water,  flowing  underground, 
complete  the  disorganisation  of  the  vegetable 
matter,  and  consolidate  the  whole. 

"  The  climate  of  the  southern  part  of  America 
appears  particularly  favourable  to  the  production 
of  peat.  In  the  Falkland  Islands  almost  every 
kind  of  plant,  even  the  coarse  grass  which  covers 
the  whole  surface  of  the  land,  becomes  converted 
into  this  substance :  scarcely  any  situation  checks 
its  growth ;  some  of  the  beds  are  as  much  as 
twelve  feet  thick,  and  the  lower  part  becomes  so 
solid  when  dry  that  it  will  hardly  burn.  Although 
every  plant  lends  its  aid,  yet  in  most  parts  the 
Astelia  is  the  most  efficient. 

"  It  is  rather  a  singular  circumstance,  as  being 
so  very  different  from  what  occurs  in  Europe, 
that  I  nowhere  saw  moss  forming  by  its  decay 
any  portion  of  the  peat  in  South  America.  With 
respect  to  the  northern  limit  at  which  the  climate 
allows  of  that  peculiar  kind  of  slow  decomposition 
which  is  necessary  for  its  production,  I  believe 
that  in  Chiloe  (lat.  41°  to  42°),  although  there  is 
much  swampy  ground,  no  well  characterised  peat 
occurs;  but  in  the  Chonos  Islands,  three  degrees 
farther  southward,  we  have  seen  that  it  is  abun- 
dant. On  the  eastern  coast  in  La  Plata  (lat.  35°) 
I  was  told  by  a  Spanish  resident,  who  had  visited 
Ireland,  that  he  had  often  sought  for  this  sub- 
stance, but  had  never  been  able  to  find  any.  He 
showed  me,  as  the  nearest  approach  to  it  which 
he  had  discovered,  a  black  peaty  soil,  so  pene- 
trated with  roots  as  to  allow  of  an  extremely  slow 
and  imperfect  combustion." 

^  J  The  next  stage  in  the  making  of  coal  is  one  in 

4~ ymich  the  change  has  proceeded  a  long  way  from 

/the   starting-point.      Lignite  is    the   name  which 


72  THE   STORY  OF  A   PIECE   OF  COAL. 

has  been  applied  to  a  form  of  impure  coal,  which 
sometimes  goes  under  the  name  of  "  brown  coal." 
It  is  not  a  true  coal,  and  is  a  very  long  way  from 
that  final  stage  to  which  it  must  attain  ere  it  takes 
rank  with  the  most  valuable  of  earth's  products. 
From  the  very  commencement,  an  action  has 
been  going  on  which  has  caused  the  amount  of 
the  gaseous  constituents  to  become  less  and  less, 
and  which  has  consequently  caused  the  carbon 
remaining  behind  to  occupy  an  increasingly  large 
proportion  of  the  whole  mass.  So,  when  we 
arrive  at  the  lignite  stage,  we  find  that  a  consid- 
erable quantity  of  volatile  matter  has  already 
been  parted  with,  and  that  the  carbon,  which  in 
ordinary  living  wood  is  about  50  per  cent,  of  the 
whole,  has  already  increased  to  about  67  per  cent. 
In  most  lignites  there  is,  as  a  rule,  a  comparatively 
large  proportion  of  sulphur,  and  in  such  cases  it 
is  rendered  useless  as  a  domestic  fuel.  It  has 
been  used  as  a  fuel  in  various  processes  of  manu- 
facture, and  the  lignite  of  the  well-known  Bovey 
Tracey  beds  has  been,  utilised  in  this  way  at  the 
neighbouring  potteries.  As  compared  with  true 
coal,  it  is  distinguished  by  the  abundance  of 
smoke  which  it  produces  and  the  choking  sul- 
phurous fumes  which  also  accompany  its  combus- 
tion, but  it  is  largely  used  in  Germany  as  a  useful 
source  of  paraffin  and  illuminating  oils.  In 
Silesia,  Saxony,  and  in  the  district  about  Bonn, 
large  quantifies  of  lignite  are  mined,  and  used  as 
fuel.  Large  stores  of  lignite  are  known  to  exist 
in  the  Weald  of  the  south-east  of  England,  and 
although  the  mining  operations  which  were  car- 
ried on  at  one  time  at  Heathfield,  Bexhill,  and 
other  places,  were  failures  so  far  as  the  actual 
discovery  of  true  coal  was  concerned,  yet  there 


VARIOUS  FORMS  OF  COAL  AND  CARBON.   73 

can  be  no  doubt  as  to  the  future  value  of  the 
lignite  in  these  parts,  when  England's  supplies  of 
coal  approach  exhaustion,  and  attention  is  turned 
to  other  directions  for  the  future  source  of  her 
gas  and  paraffin  oils. 

The  tertiary  coals  of  America,  found  in  Nevada, 
Oregon,  and  the  Saskatchewan  region,  and  even 
some  of  those  of  cretaceous  age,  are  classed  as  lig- 
nite. The  more  perfect  coals  are,  however,  so 
abundant  and  accessible  in  the  United  States 
that  lignite  is  mined  and  used  only  in  localities 
remote  from  the  anthracite  and  bituminous  fields. 

We  have  now  closely  approached  to  true  coal, 
and  the  next  step  which  we  shall  take  will  be  to 
consider  the  varieties  in  which  the  black  mineral 
itself  is  found.  The  principal  of  these  varieties 
are  as  follows,  against  each  being  placed  the 
average  proportion  of  pure  carbon  which  it  con- 
tains :  — 

Cannel,  Candle,  or  Parrott  Coal,  84  per  cent.  ; 

Bituminous,  or  Soft  Coal,  88  per  cent.,  shading 
through  Semi-Bituminous  and  Semi-  Anthra- 
cite to 

Anthracite,  Blind  Coal,  Culm,  Glance,  or  Stone 
Coal,  93  per  cent. 

As  far  as  the  gas-making  properties  of  the  first 
two  are  concerned,  the  relative  prpportions^of 
carbon  and  volatile  products  are  much  the  same. 
Everybody  knows  a  piece  of  cannel  coal  when  it 
is  seen,  how  it  appears  almost  to  have  been  once 
in  a  molten  condition,  and  how  it  breaks  with  a 
conchaidaj  fracture,  as  opposed  to  the  cleavage 
oTn^irurnin 


coal  into  thin  layers;  and,  most 
apparent  and  most  noticeable  of  all,  how  it  does 
not  soil  the  hands  after  the  manner  of  ordinary 
coal.  It  is  at  times  so  dense  and  compact  that 


74  THE  STORY  OF  A  PIECE  OF  COAL. 

it  has  been  fashioned  into  ornaments,  and  is  ca- 
pable of  receiving  a  polish  like  jet.  From  the 
large  percentage  of  volatile  products  which  it 
contains,  it  is  greatly  used  in  English  gasworks. 

The  highly  bituminous,  "  fat,"  or  "  caking" 
coals  when  heated  become  plastic  and  give  off 
much  gas.  If  the  mass  is  not  allowed  to  burn 
a  porous  product  is  left  which  is  known  as  coke. 
In  the  iron  regions  the  gas  is  burnt  off  from  great 
quantities  of  this  coal  in  kilns,  so  as  to  obtain  the 
coke  for  the  iron  furnaces.  The  same  kind  of 
coal  is  also  brought  into  cities  where  the  gas  is 
carefully  distilled  off  and  collected  while  the  coke 
is  disposed  of  as  a  bye-product.  The  grades  be- 
tween caking  coal  and  anthracite  are  especially 
valuable  for  the  rapid  production  of  steam,  as 
is  required  in  locomotives,  and  hence  are  often 
called  "  steam  "  coals.  These  more  or  less  bi- 
tuminous varieties  are  commonly  used  in  Eng- 
land and  the  central  parts  of  the  United  States 
for  domestic  purposes.  North  and  east  of  Penn- 
sylvania anthracite  is  the  domestic  coal.  The 
more  coal  approaches  the  character  of  anthracite 
the  more  difficult  it  is  to  get  it  to  burn,  but 
when  at  last  fairly  alight  it  gives  out  great  heat, 
and  what  is  more  important,  a  less  quantity  of 
gas,  smoke,  ammonia,  sulphurous  fumes,  and  ash. 
It  is  thus  an  admirable  fuel  for  household  pur- 
poses, and  with  hot  blast  it  may  be  used  in  iron- 
smelting  furnaces.  In  the  Eastern  States  soft 
coal  is  familiar  only  in  the  blacksmith's  forge. 

It  is  a  significant  fact  and  one  which  proves 
that  the  various  kinds  of  coal  which  are  found 
are  nothing  but  stages  begotten  by  different  de- 
grees of  disentanglement  of  the  contained  gases, 
that  where,  as  in  some  parts,  a  mass  of  basalt  has 


VARIOUS  FORMS  OF  COAL  AND  CARBON.   75 

come  into  contact  with  ordinary  bituminous  coal, 
the  coal  has  assumed  the  character  of  anthracite, 
whilst  the  change  has  in  some  instances  gone  so 
far  as  to  convert  the  anthracite  into  graphite. 
The  basalt,  which  is  one  of  the  igneous  rocks, 
has  been  erupted  into  the  coal-seam  in  a  state 
of  fusion,  and  the  heat  contained  in  it  has  been 
sufficient  to  cause  the  disentanglement  of  the 
gases,  the  extraction  of  which  from  the  coal 
brings  about  the  condition  of  anthracite  and 
graphite. 

The  mention  of  graphite  brings  us  to  the  next 
stage.  Graphite,  plumbago,  or,  as  it  is  more 
commonly  called,  black  lead,  which  we  may  say 
in  passing,  has  nothing  of  lead  about  it  at  all,  is 
best  known  in  the  shape  of  that  very  useful  and 
cosmopolitan  article,  the  black-lead  pencil.  This 
is  even  purer  carbon  than  anthracite,  not  more 
than  5  per  cent,  of  ash  and  other  impurities  being 
present.  It  is  well  known  by  its  grey  metallic 
lustre ;  the  chemist  uses  it  mixed  with  fire-clay 
to  make  his  crucibles;  the  engineer  uses  it,  finely 
powdered,  to  lubricate  his  machinery  ;  the  house- 
keeper uses  it  to  "  blacklead  "  her  stoves  to  pre- 
vent them  from  rusting.  An  imperfect  graphite 
is  found  inside  some  of  the  hottest  retorts  from 
which  gas  is  distilled,  and  this  is  used  as  the  nega- 
tive element  in  zinc  and  carbon  electricity-making 
cells,  whilst  its  use  as  the  electrodes  or  carbons 
of  the  arc-lamp  is  becoming  more  and  more  widely 
adopted,  as  installations  of  electric  light  become 
more  general. 

Over  a  million  pounds  of  graphite  are  mined 
yearly  at  Ticonderoga,  N.  Y.,  and  a  small  quantity 
is  obtained  in  Berks  County,  Pa.  This  output 
supplies  only  about  5  per  cent,  of  the  domestic 


76  THE   STORY   OF  A   PIECE   OF   COAL. 

demand.  Germany  produces  a  considerable  quan- 
tity of  this  mineral,  but  the  bulk  of  the  world's 
supply  comes  from  Ceylon.  Extensive  deposits 
of  graphite  are  found  in  rocks  of  the  Laurentian 
age  in  Canada.  In  this  formation  nothing  which 
can  undoubtedly  be  classed  as  organic  has  yet 
been  discovered.  Life  at  this  early  period  must 
have  found  its  home  in  low  and  humble  forms  and 
if  the  eozoon  of  Dawson,  which  has  been  thought 
to  represent  the  earliest  types  of  life,  turns  out 
after  all  not  to  be  organic,  but  only  a  deceptive 
appearance  assumed  by  certain  of  the  strata,  we 
at  least  know  that  it  must  have  been  in  similarly 
humble  forms  that  life,  if  it  existed  at  all,  did 
then  exist.  We  can  scarcely,  therefore,  expect 
that  the  vegetable  world  had  made  any  great 
advance  in  complexity  of  organism  at  this  time, 
otherwise  the  supplies  of  graphite  or  plumbago 
which  are  found  in  the  formation,  would  be 
attributed  to  dense  forest  growths,  acted  upon, 
after  death,  in  a  similar  manner  to  that  which 
awaited  the  vegetation  which,  ages  after,  went 
to  form  beds  of  coal.  At  present  we  know  of 
no  source  of  carbon  except  through  the  interven- 
tion and  the  chemical  action  of  plants.  Like 
iron,  carbon  is  seldom  found  on  the  earth  except 
in  combination.  If  there  were  no  growth  of 
vegetation  at  this  far-away  period  to  give  rise 
to  these  deposits  of  graphite,  we  are  compelled 
to  ask  ourselves  whether,  perchance,  there  did  not 
then  exist  conditions  of  which  we  are  not  now 
cognisant  on  the  earth,  and  which  allowed 
graphite  to  be  formed  without  assistance  from 
the  vegetable  kingdom.  At  present,  however, 
science  is  in  the  dark  as  to  any  other  process  of 
its  formation,  and  we  are  left  to  assume  that  the 


VARIOUS  FORMS  OF  COAL  AND  CARBON.   77 

vegetable  growth  of  the  time  was  enormous  in 
quantity,  although  there  is  nothing  to  show  the 
kind  of  vegetation,  whether  humble  mosses  or 
tall  forest  trees,  which  went  to  constitute  the 
masses  of  graphite.  Geologists  will  agree  that 
this  is  no  small  assumption  to  make,  since,  if 
true,  it  may  show  that  there  was  an  abundance 
of  vegetation  at  a  time  when  animal  life  was 
hidden  in  one  or  more  very  obscure  forms,  one 
only  of  which  has  so  far  been  detected,  and 
whose  very  identity  is  strongly  doubted  by  nearly 
all  competent  judges.  At  the  same  time  there  may 
have  been  an  abundance  of  both  animal  and  vege- 
table life  at  the  time.  We  must  not  forget  that 
it  is  a  well-ascertained  fact  that 
in  later  ages,  the  minute  seed- 
spores  of  forest  trees  were  in 
such  abundance  as  to  form  im- 
portant seams  of  coal  in  the 
true  carboniferous  era,  the  trees 
which  gave  birth  to  them  being 
now  classed  amongst  the  hum- 
ble cryptogams,  the  ferns,  and 
club-mosses,  &c.  The  graphite 
of  Laurentian  age  may  not  im- 
probably have  been  caused  by 
deposits  of  minute  portions  of 
similar  lowly  specimens  of  vege- 
table life,  and  if  the  eozoon,  the 
"  dawn-animalcule,"  does  repre- 
sent the  animal  life  of  the  time, 
life  whose  types  were  too  minute 
to  leave  undoubted  traces  of  their  existence,  both 
animal  life  and  vegetable  life  maybe  looked  upon 
as  existing  side  by  side  in  extremely  humble 
forms,  neither  as  yet  having  taken  an  undoubted 


FIG.  30.— Z  . 
dron.  Portion  of 
Sandstone  stem  af- 
ter removal  of  bark 
of  a  giant  club- 
moss. 


78  THE  STORY  OF  A   PIECE  OF  COAL. 

step  forward  in  advance  of  the  other  in  respect 
to  complexity  of  organism. 

There  is  but  one  more  form  of  carbon  with 
which  we  have  to  deal  in  running  through  the 
series.  We  have  seen  that  coal  is  not  the  sum- 
mum  bonum  of  the  series.  Other  transformations 
take  place  after  the  stage  of  coal  is  reached, 
which,  by  the  continued  disentanglement  of  gases, 
finally  bring  about  the  plumbago  stage. 

What  the  action  is  which  transforms  plumbago 
or  some  other  form  of  carbon  into  the  condition 
of  a  diamond  cannot  be  stated.  Diamond  is  the 
purest  form  of  carbon  found  in  nature.  It  is  a 
beautiful  object,  alike  from  the  results  of  its 
powers  of  refraction,  as  also  from  the  form  into 
which  its  carbon  has  been  crystallised.  How 
Nature,  in  her  wonderful  laboratory,  has  precipi- 
tated the  diamond,  with  its  wonderful  powers  of 
spectrum  analysis,  we  cannot  say  with  certainty. 
Certain  chemists  have,  at  a  great  expense,  pro- 
duced crystals,  which,  in  every  respect,  stand 
the  tests  of  true  diamonds;  but  the  process  of 
their  production  at  a  great  expense  has  in  no 
way  diminished,  the  value  of  the  natural  pro- 
duct. 

The  process  by  which  artificial  diamonds  have 
been  produced  is  so  interesting,  and  the  subject 
may  prove  to  be  of  so  great  importance,  that  a 
few  remarks  upon  the  process  may  not  be  unac- 
ceptable. 

The  experiments  of  the  great  French  chemist, 
Dumas,  and  others,  satisfactorily  proved  the  fact, 
which  has  ever  since  been  considered  thoroughly 
established,  that  the  diamond  is  nothing  but  car- 
bon crystallised  in  nearly  a  pure  state,  and  many 
chemists  have  since  been  engaged  in  the  hitherto 


VARIOUS  FORMS  OF  COAL  AND  CARBON.   79 

atile  endeavour  to  turn  ordinary  carbon  into  the 
true  diamond. 

Despretz  at  one  time  considered  that  he  had 
discovered  the  process,  which  consisted  in  his  case 

submitting  a  piece  of  charcoal  to  the  action  of 
in  electric  battery,  having  in  his  mind  the  similar 
Drocess  of  electrolysis,  by  which  water  is  divided, 
up  into  the  two  gases,  hydrogen  and  oxygen.  Mp 
obtained  a  microscopic  deposit  on  the  poles  of 
the  battery,  which  he  pronounced  to  be  diamond 
dust,  but  which,  a  long  time  after,  was  proved  to 
be  nothing  but  graphite  in  a  crystallised  state. 
This  was,  however,  certainly  a  step  in  the  right 
direction. 

The  honour  of  first  accomplishing  the  task 
fell  to  Mr.  Hannay,  of  Glasgow,  who  succeeded 
in  producing  very  small  but  comparatively  soft 
diamonds,  by  heating  lampblack  under  great 
pressure,  in  company  with  one  or  two  other  in- 
gredients. The  process  was  a  costly  one,  and 
beyond  being  a  great  scientific  feat,  the  discovery 
led  to  little  result. 

A  young  French  chemist,  M.  Henri  Moissan, 
has  since  come  to  the  front,  and  the  diamonds 
which  he  has  produced  have  stood  every  test  for 
the  true  diamond  to  which  they  could  be  subjected ; 
above  all,  the  density  of  the  product  is  3.5,  /.  ^., 
that  of  the  diamond,  that  of  graphite  reaching  2 
only. 

He  recognised  that  in  all  diamonds  which  he 
had  consumed- — and  he  consumed  some  ^150 
worth  in  order  to  assure  himself  of  the  fact — • 
there  were  always  traces  of  iron  in  their  composi- 
tion. He  saw  that  iron  in  fusion,  like  other 
metals,  always  dissolves  a  certain  quantity  of  car- 
bon. Might  it  not  be  that  molten  iron,  cooling 


8o  THE   STORY  OF  A   PIECE  OF  COAL. 

in  the  presence  of  carbon,  deep  in  volcanic  depths 
where  there  was  little  scope  for  the  iron  to  ex- 
pand in  assuming  the  solid  form,  would  exert 
such  tremendous  pressure  upon  the  particles  of 
carbon  which  it  absorbed,  that  these  would  assume 
the  crystalline  state  ? 

He  packed  a  cylinder  of  soft  iron  with  the 
carbon  of  sugar,  and  placed  the  whole  in  a  cruci- 
ble filled  with  molten  iron,  which  was  raised  to  a 
temperature  of  3000°  by  means  of  an  electric  fur- 
nace. The  soft  cylinder  melted,  and  dissolved 
a  large  portion  of  the  carbon.  The  crucible  was 
thrown  into  wTater,  and  a  mass  of  solid  iron  was 
formed.  It  was  allowed  further  to  cool  in  the 
open  air,  but  the  expansion  which  the  iron  would 
have  undergone  on  cooling,  was  checked  by  the 
crucible  which  contained  it.  The  result  was  a 
tremendous  pressure,  during  which  the  carbon, 
which  was  still  dissolved,  was  crystallised  into 
minute  diamonds. 

These  showed  themselves  as  minute  points 
which  were  easily  separable  from  the  mass  by  the 
action  of  acids.  Thus  the  wonderful  trlinsforma- 
tion  from  sugar  to  the  diamond  was  accomplished. 

It  should  be  mentioned  that  iron  is  one  of  the 
few  substances  that  possess  the  peculiar  property 
of  expanding  when  passing  from  the  liquid  to  the 
solid  state. 

The  diamonds  so  obtained  were  of  both  kinds. 
The  particles  of  white  diamond  resembled  in 
every  respect  the  true  brilliant.  But  there  was 
also  an  appreciable  quantity  of  the  variety  known 
as  the  "  black  diamond."  These  diamonds  seem 
to  approximate  more  closely  to  carbon  as  we  are 
most  familiar  with  it.  They  are  not  considered 
as  of  such  value  as  the  transparent  form,  but 


VARIOUS  FORMS  OF  COAL  AND  CARBON.   8 1 

they  are  still  of  considerable  commercial  value. 
The  carbonado,  as  this  kind  is  called,  possesses  so 
great  a  degree  of  hardness  that  by  means  of  it  it 
is  possible  to  bore  through  the  hardest  rocks. 
The  diamond  drill,  used  for  boring  purposes,  is 
furnished  around  the  outer  edge  of  the  cylinder 
of  the  "  boring  bit,"  as  it  is  called,  with  perhaps 
a  dozen  black  diamonds,  together  with  another 
row  of  Brazilian  diamonds  on  the  inside.  By  the 
rotation  of  the  boring  tool  the  sharp  edges  of  the 
diamonds  cut  their  way  through  rocks  of  all  de- 
grees of  hardness,  leaving  a  core  of  the  rock  cut 
through,  in  the  centre  of  the  cylindrical  drill.  It 
is  found  that  the  durability  of  the  natural  edge  of 
the  diamond  is  far  greater  than  that  of  the  edge 
caused  by  artificial  cutting  and  trimming.  The 
cutting  of  a  pane  of  glass  by  means  of  a  ring  set 
with  an  artificially  cut  diamond,  cannot  therefore 
be  done  without  injuring  to  a  slight  extent  the 
edge  of  the  stone. 

The  diamond  is  the  hardest  of  all  known 
substances,  leaving  a  scratch  on  any  substance 
across  which  it  may  be  drawn.  Yet  it  is  one 
whose  form  can  be  changed,  and  whose  hardness 
can  be  completely  destroyed,  by  the  simple  process 
of  combustion.  It  can  be  deprived  of  its  high 
lustre,  and  of  its  power  of  breaking  up  by  refrac- 
tion the  light  of  the  sun  into  the  various  tints  of 
the  solar  spectrum,  simply  by  heating  it  to  a  red 
heat,  and  then  plunging  it  into  a  jar  of  oxygen 
gas.  It  immediately  expands,  changes  into  a 
coky  mass,  and  burns  away.  The  product  left 
behind  is  a  mixture  of  carbon  and  oxygen,  in  the 
proportions  in  which  it  is  met  with  in  carbonic- 
anhydride,  or,  carbonic  acid  gas  deprived  of  its 
water.  This  is  indeed  a  strange  transformation, 
6 


82  THE   STORY  OF  A   PIECE   OF  COAL. 

from  the  most  valuable  of  all  our  precious  stones 
to  a  compound  which  is  the  same  in  chemical  con- 
stituents as  the  poisonous  gas  which  we  and  all 
animals  exhale.  But  there  is  this  to  be  said. 
Probably  in  the  far-away  days  when  the  diamond 
began  to  be  formed,  the  tree  or  other  vegetable 
product  which  was  its  far-removed  ancestor  ab- 
stracted carbonic  acid  gas  from  the  atmosphere, 
just  as  do  our  plants  in  the  present  day.  By  this 
means  it  obtained  the  carbon  wherewith  to  build 
up  its  tissues.  Thus  the  combustion  of  the  dia- 
mond into  carbonic-anhydride  now  is,  after  all, 
only  a  return  to  the  same  compound  out  of  which 
it  was  originally  formed.  How  it  was  formed  is 
a  secret ;  probably  the  time  occupied  in  the  for- 
mation of  the  diamond  may  be  counted  by  centu- 
ries, but  the  time  of  its  re-transformation  into  a 
mass  of  coky  matter  is  but  the  work  of  seconds  ! 

There  is  another  form  of  carbon  which  was 
formerly  of  much  greater  importance  than  it  is 
now,  and  which,  although  not  a  natural  product, 
is  yet  deserving  of  some  notice  here.  Charcoal 
is  the  substance  referred  to. 

In  early  days  the  word  "  coal,"  or,  as  it  was 
also  spelt,  "  cole,"  was  applied  to  any  substance 
which  was  used  as  fuel ;  hence  we  have  a  refer- 
ence in  the  Bible  to  a  "  fire  of  coals,"  so  trans- 
lated when  the  meaning  to  be  conveyed  was  prob- 
ably not  coal  as  we  know  it.  Wood  was  formerly 
known  as  coal,  whilst  charred  wood  received  the 
name  of  charred  coal,  which  was  soon  corrupted 
into  charcoal.  The  charcoal-burners  of  years 
gone  by  were  a  far  more  flourishing  community 
than  they  are  now.  When  the  old  baronial  halls 
and  country-seats  depended  on  them  for  the  basis 
of  their  fuel,  and  the  log  was  a  more  frequent 


VARIOUS  FORMS  OF  COAL  AND  CARBON.   83 

occupant  of  the  fire-grate  than  now,  these  occu- 
piers of  midforest  were  a  people  of  some  impor- 
tance. 

We  must  not  overlook  the  fact  that  there  is 
another  form  of  charcoal,  namely,  animal  char- 
coal or  bone-black.  This  can  be  obtained  by 
heating  bones  to  redness  in  closed  iron  vessels.- 
In  the  refining  of  raw  sugar  the  decoloration  of 
the  syrup  is  brought  about  by  filtering  it  through 
animal-charcoal;  by  this  means  the  syrup  is  ren- 
dered colourless. 

When  properly  prepared,  charcoal  exhibits 
very  distinctly  the  rings  of  annual  growth  which 
may  have  characterised  the  wood  from  which  it 
was  formed.  It  is  very  light  in  consequence  of 
its  porous  nature,  and  it  is  wonderfully  indestruc- 
tible. 

•"But  its  greatest,  because  it  is  its  most  useful 
property,  is  undoubtedly  the  power  which  it  has 
of  absorbing  great  quantities  of  gas  into  itself. 
It  is  in  fact  what  may  be  termed  an  all-round 
purifier.  It  is  a  deodoriser,  a  disinfectant,  and  a 
decoloriser.  It  is  an  absorbent  of  bad  odours, 
and  partially  removes  the  smell  from  tainted 
meat.  It  has  been  used  when  offensive  manures 
have  been  spread  over  soils,  with  the  same  object 
in  view,  and  its  use  for  the  purification  of  water 
is  well  known  to  all  users  of  filters.  Some  idea 
of  its  power  as  a  disinfectant  may  be  gained  by 
the  fact  that  one  volume  of  wood-charcoal  will 
absorb  no  less  than  90  volumes  of  ammonia,  35 
volumes  of  carbonic  anhydride,  and  65  volumes 
of  sulphurous  anhydride. 

Other  forms  of  carbon  which  are  well-know^ 
are  (i)  coke,  the  residue  left  when  coal  has  been\ 
subjected  to  a  great  heat  in  a  closed  retort ;  (2) 


84  THE   STORY   OF  A   PIECE   OF   COAL. 

soot  and  lamp-black,  the  former  of  which  is  use- 
ful as  a  manure  in  consequence  of  ammonia  being 
present  in  it,  whilst  the  latter  is  a  specially  pre- 
pared soot,  and  is  used  chiefly  as  the  colouring 
matter  of  black  paint  and  as  the  basis  of  Indian 
ink  and  printers'  ink. 


CHAPTER   IV. 

THE    COAL-MINE    AND    ITS    DANGERS. 

IT  is  somewhat  strange  to  think  that  where 
once  existed  the  solitudes  of  an  ancient  carbon- 
iferous forest  now  is  the  site  of  a  busy  under- 
ground town.  For  a  town  it  really  is.  The  vari- 
ous roads  and  passages  which  are  cut  through  the 
solid  coal  as  excavation  of  a  coal-mine  proceeds, 
represent  to  a  stranger  all  the  intricacies  of  a 
well-planned  town.  Nor  is  the  extent  of  these 
underground  towns  a  thing  to  be  despised.  There 
is  an  old  pit  near  Newcastle  which  contains  not 
less  than  fifty  miles  of  passages.  Other  pits 
there  are  whose  main  thoroughfares  in  a  direct 
line  are  not  less  than  four  or  five  miles  in  length, 
and  this,  it  must  be  borne  in  mind,  is  the  result  of 
excavation  wrought  by  human  hands  and  human 
labour. 

So  great  an  extent  of  passages  necessarily  re- 
quires some  special  means  of  keeping  the  air 
within  it  in  a  pure  state,  such  as  will  render  it  fit 
for  the  workers  to  breathe.  The  further  one 
would  go  from  the  main  thorougfare  in  such  a 
mine,  the  less  likely  one  would  be  to  find  air  of 
sufficient  purity  for  the  purpose.  It  is  as  a  con- 


THE   COAL-MINE  AND   ITS   DANGERS.  85 

sequence  necessary  to  take  some  special  steps  to 
provide  an  efficient  system  of  ventilation  through- 


FIG.  31. — Engine-House  and  Buildings  at  head  of  a  Coal- Pit. 

out  the  mine.  This  is  effectually  done  by  two 
shafts,  called  respectively  the  downcast  and  the 
upcast  shaft.  A  shaft  is  in  reality  a  very  deep 
well,  and  may  be  circular,  rectangular  or  oval  in 
form,  In  order  to  keep  out  water  which  may  be 
struck  in  passing  through  the  various  strata,  it  is 
protected  by  plank  or  wood  tubbing,  or  the  shaft 
is  bricked  over,  or  sometimes  even  cast-iron  seg- 
ments are  sunk.  In  many  shafts  which,  owing  to 
their  great  depth,  pass  through  strata  of  every 
degree  of  looseness  or  viscosity^  all  three  methods 
are  utilised  in  turn.  In  Westphalia,  where  coal  is 
worked  beneath  strata  of  more  recent  geological 
age,  narrow  shafts  have  been,  in  many  cases, 
sunk  by  means  of  boring  apparatus,  in  preference 
to  the  usual  process  of  excavation,  and  the  prac- 
tice has  since  been  adopted  in  South  Wales.  In 
England  the  usual  form  of  the  pit  is  circular,  but 
elliptical  and  rectangular  pits  are  also  in  use.  On 
the  Continent  polygonal-shaped  shafts  are  not 


86  THE   STORY  OF   A   PIECE   OF   COAL. 

uncommon,  while  in  America  they  are  usually 
rectangular,  measuring  about  twelve  by  thirty 
feet,  and  divided  into  a  pump-way,  two  carriage- 
ways, and  an  air-way. 

If  there  be  one  of  these  shafts  at  one  end  of 
the  mine,  and  another  at  a  remote  distance  from 
it,  a  movement  of  the  air  will  at  once  begin,  and 
a  rough  kind  of  ventilation  will  ensue.  This  is, 
however,  quite  insufficient  to  provide  the  neces- 
sary quantity  of  air  for  inhalation  by  the  army 
of  workers  in  the  coal-mine,  for  the  current  thus 
set  up  does  not  even  provide  sufficient  force  to 
remove  the  effete  air  and  impurities  which  ac- 
cumulate from  hundreds  of  perspiring  human 
bodies. 

It  is  therefore  necessary  to  introduce  some 
artificial  means,  by  which  a  strong  and  regular 
current  shall  pass  down  one  shaft,  through  the 
mine  in  all  its  workings,  and  out  at  the  other 
shaft.  This  is  accomplished  in  various  ways.  It 
took  many  years  before  those  interested  in  mines 
came  thoroughly  to  understand  how  properly  to 
secure  ventilation,  and  in  bygone  days  the  system 
was  so  thoroughly  bad  that  a  tremendous  amount 
of  sickness  prevailed  amongst  the  miners,  owing 
to  the  poisonous  effects  of  breathing  the  same  air 
over  and  over  again,  charged,  as  it  was,  with 
more  or  less  of  the  gases  given  off  by  the  coal 
itself.  Now,  those  miners  who  do  so  great  a  part 
in  furnishing  the  means  of  warming  our  houses  in 
winter,  have  the  best  contrivances  which  can  be 
devised  to  furnish  them  with  an  everflowing  cur- 
rent of  fresh  air. 

Amongst  the  various  mechanical  appliances 
which  have  been  used  to  ensure  ventilation  may 
be  mentioned  pumps,  fans,  and  pneumatic  screws. 


THE   COAL-MINE  AND   ITS   DANGERS.  87 


There  is,  as  we  have  said,  a  certain,  though  slight, 
movement  of  the  air  in  the  two  columns  which 
constitute  the  upcast  and  the  downcast  shafts, 
but  in  order  that  a  current  may  flow  which  shall 
be  equal  to  the  necessities  of  the  miners,  some 
means  are  necessary  by  which  this  condition  of 
almost  equilibrium  shall  be  considerably  dis- 
turbed, and  a  current  created  which  shall  sweep 
all  foul  gases  before  it.  One  plan  was  to  force 
fresh  air  into  the  downcast,  which  should  in  a 
sense  push  the  foetid  air  away  by  the  upcast,  and 
so  draw  the  gases  in  the  train  of  the  exhausted 
air.  In  other  cases  the  plan  was  adopted  of  pro- 
viding a  continual  falling  of  water  down  the  down- 
cast shaft. 

These  various  plans  have  almost  all  given 
way  to  that  which  is  the  most  serviceable  of  all, 
namely,  the  plan  of  having  an  immense  furnace 
constantly  burning  in  a  specially-constructed 
chamber  at  the  bottom  of  the  upcast.  By  this 
means  the  column  of  air  above  it  becomes  rarefied 
under  the  heat,  and  ascends,  whilst  the  cooler  air 
from  the  downcast  rushes  in  and  spreads  itself  in 
all  directions  whence  the  bad  air  has  already  been 
drawn.  On  the  other  hand,  to  so  great  a  state  of 
perfection  have  ventilating  fans  been  brought, 
that  one  was  recently  erected  which  would  be 
capable  of  changing  the  air  of  Westminster  Hall 
thirty  times  in  one  hour. 

Having  procured  a  current  of  sufficient  power, 
it  will  be  at  once  understood  that,  if  left  to  its 
own  will,  it  would  take  the  nearest  path  which 
might  lie  between  its  entrance  and  its  exit,  and, 
in  this  way,  ventilating  the  principal  street  only, 
would  leave  all  the  many  off-shoots  from  it  undis- 
turbed. It  is  consequently  manipulated  by  means 


88  THE   STORY  OF  A   PIECE   OF   COAL. 

of  barriers  and  tight-fitting  doors,  in  such  a  way 
that  the  current  is  bound  in  turn  to  traverse  every 
portion  of  the  mine.  A  large  number  of  boys, 
known  as  trappers,  are  employed  in  opening  the 
doors  to  all  comers,  and  in  carefully  closing  the 
doors  immediately  after  they  have  passed,  in 
order  that  the  current  may  not  circulate  through 
passages  along  which  it  is  not  intended  that  it 
should  pass. 

The  greatest  dangers  which  await  the  miners 
are  those  which  result,  in  the  form  of  terrible  ex- 
plosions, from  the  presence  of  inflammable  gases 
in  the  mines.  The  great  walls  of  coal  which 
bound  the  passages  in  mines  are  constantly  ex- 
uding supplies  of  gas  into  the  air.  When  a  bank 
of  coal  is  brought  down  by  an  artificial  explosion, 
by  dynamite,  by  lime  cartridges,  or  by  some 
other  agency,  large  quantities  of  gas  are  some- 
times disengaged,  and  not  only  is  this  highly  det- 
rimental to  the  health  of  the  miners,  if  not  car- 
ried away  by  proper  ventilation,  but  it  constitutes 
a  constant  danger  which  may  at  any  time  cause 
an  explosion  when  a  naked  light  is  brought  into 
contact  with  it.  Fire-damp  may  be  sometimes 
heard  issuing  from  fiery  seams  with  a  peculiar 
hissing  sound.  If  the  volume  be  great,  the  gas 
forms  what  is  called  a  blower,  and  this  often  hap- 
pens in  the  neighbourhood  of  a  fault.  When  coal 
is  brought  down  in  any  large  volume,  the  blowers 
which  commence  may  be  exhausted  in  a  few  mo- 
ments. Others,  however,  have  been  known  to 
last  for  years,  this  being  the  case  at  Wallsend, 
where  the  blower  gave  off  120  feet  of  gas  per 
minute.  In  such  cases  the  gas  is  usually  con- 
veyed in  pipes  to  a  place  where  it  can  be  burned 
in  safety. 


«*; 


PHE   COAL-MINE  AND   ITS   DANGERS.  89 


In  the  early  days  of  coal-mining  the  ex- 
plosions caused  by  this  gas  soon  received  the 
serious  attention  of  the  scientific  men  of  the  age. 
In  the  Philosophical  Transactions  of  the  Royal 
Society we  find  a  record  of  a  gas  explosion  in  1677. 
The  amusing  part  of  such  records  was  that  the 
explosions  were  ascribed  by  the  miners  to  sup- 
ernatural agencies.  Little  attention  seemed  to 
have  been  paid  to  the  fact,  which  has  since  so 
thoroughly  been  established,  that  the  explosions 
were  caused  by  accumulations  of  gas,  mixed  in 
certain  proportions  with  air.  As  a  consequence, 
tallow  candles  with  an  exposed  flame  were  freely 
used,  especially  in  Britain.  These  were  placed  in 
niches  in  the  workings,  where  they  would  give  to 
the  pitman  the  greatest  amount  of  light.  Previ- 
ous to  the  introduction  of  the  safety-lamp,  work- 
ings were  tested  before  the  men  entered  them,  by 
"  trying  the  candle."  Owing  to  the  specific 
gravity  of  fire-damp  (.555)  being  less  than  that  of 
air,  it  always  finds  a  lodgment  at  the  roofs  of 
the  workings,  so  that,  to  test  the  condition  of  the 
air,  it  was  necessary  to  steadily  raise  the  candle 
to  the  roof  at  certain  places  in  the  passages,  and 
watch  carefully  the  action  of  the  flame.  The 
presence  of  fire-damp  would  be  shown  by  the 
flame  assuming  a  blue  colour,  and  by  its  elonga- 
tion ;  the  presence  of  other  gases  could  be  de- 
tected by  an  experienced  man  by  certain  pecul- 
iarities in  the  tint  of  the  flame.  This  testing 
with  the  open  flame  has  almost  entirely  ceased 
since  the  introduction  of  the  perfected  Davy  lamp. 

The  use  of  candles  for  illumination  soon  gave 
place  in  most  of  the  large  collieries  to  the  intro- 
duction of  small  oil-lamps.  In  the  less  fiery 
mines  on  the  Continent,  oil-lamps  of  the  well- 


90  THE   STORY   OF   A   PIECE   OF   COAL. 

known  Etruscan  pattern  are  still  in  use,  whilst 
small  metal  lamps,  which  can  conveniently  be 
attached  to  the  cap  of  the  worker,  are  the  kind 
commonly  used  in  the  United  States.  These 
lamps  are  very  useful  in  getting  the  coal  from 
the  thinner  seams,  where  progress  has  to  be 
made  on  the  hands  and  feet.  At  the  close  of 
the  last  century,  as  workings  began  to  be  carried 
deeper,  and  coal  was  obtained  from  places  more 
and  more  infested  with  fire-damp,  it  soon  came 
to  be  realised  that  the  old  methods  of  illumina- 
tion would  have  to  be  replaced  by  others  of  a 
safer  nature. 

It  is  noteworthy  that  mere  red  heat  is  insuffi- 
cient in  itself  to  ignite  fire-damp,  actual  contact 
with  flame  being  necessary  for  this  purpose. 
Bearing  this  in  mind,  Spedding,  the  discoverer  of 
the  fact,  invented  what  is  known  as  the  "  steel- 
mill  "  for  illuminating  purposes.  In  this  a  toothed 
wheel  was  made  to  play  upon  a  piece  of  steel, 
the  sparks  thus  caused  being  sufficient  to  give  a 
moderate  amount  of  illumination.  It  is  found, 
however,  that  this  method  was  not  always  trust- 
worthy, and  lamps  were  introduced  by  Humboldt 
in  1796,  and  by  Clanny  in  1806.  In  these  lamps 
the  air  which  fed  the  flame  was  isolated  from  the 
air  of  the  mine  by  having  to  bubble  through  a 
liquid.  Many  miners  were  not,  however,  pro- 
vided with  these  lamps,  and  the  risks  attending 
naked  lights  went  on  as  merrily  as  ever. 

In  order  to  avoid  explosions  in  mines  which 
were  known  to  give  off  large  quantities  of  gas, 
"  fiery"  pits  as  they  are  called,  Sir  Humphry 
Davy  in  1815  invented  his  safety  lamp,  the  prin- 
ciple of  which  can  be  stated  in  a  few  words. 

If  a  piece  of  fine  wire  gauze  be  held  over  a 


THE  COAL-MINE  AND   ITS   DANGERS.  91 

gas-jet  before  it  is  lit,  and  the  gas  be  then  turned 
on,  it  can  be  lit  above  the  gauze,  but  the  flame 
will  not  pass  downwards  towards  the  source  of 
the  gas;  at  least,  not  until  the  gauze  has  become 
over-heated.  The  metallic  gauze  so  rapidly  con- 
ducts away  the  heat,  that  the  temperature  of  the 
gas  beneath  the  gauze  is  unable  to  arrive  at  the 
point  of  ignition.  In  the  safety-lamp  the  little 
oil-lamp  is  placed  in  a  circular  funnel  of  fine 
gauze,  which  prevents  the  flame  from  passing 
through  it  to  any  explosive  gas  that  may  be 
floating  about  outside,  but  at  the  same  time  al- 
lows  the  rays  of  light  to  pass  through  readily. 
Sir  Humphry  Davy,  in  introducing  his  lamp,  cau- 
tioned  the  miners  against  exposing  it  to  a  rapid 
current  of  air,  which  would  operate  in  such  a 
way  as  to  force  the  flame  through  the  gauze, 
and  also  against  allowing  the  gauze  to  become 
red-hot.  In  order  to  minimize,  as  far  as  possible, 
the  necessity  of  such  caution  the  lamp  has  been 
considerably  modified  since  first  invented,  the 
speed  of  the  ventilating  currents  not  now  allow- 
ing  of  the  use  of  the  simple  Davy  lamp,  but  the 
principle  is  the  same. 

During  the  progress  of  Sir  Humphry  Davy's 
experiments,  he  found  that  when  fire-damp  was 
diluted  with  85  per  cent,  of  air,  and  any  less 
proportion,  it  simply  ignited  without  explosion. 
With  between  85  per  cent,  and  89  per  cent,  of 
air,  fire-damp  assumed  its  most  explosive  form, 
but  afterwards  decreased  in  explosiveness,  until 
with  94!  per  cent,  of  air  it  again  simply  ignited 
without  explosion.  With  between  n  and  12  per 
cent,  of  fire-damp  the  mixture  was  most  danger- 
ous. Pure  fire-damp  itself,  therefore,  is  not  dan- 
gerous, so  that  when  a  small  quantity  enters  the 


92 


THE   STORY  OF  A   PIECE   OF   COAL, 


gauze  which  surrounds  the  Davy  lamp,  it  simply 
burns  with  its  characteristic  blue  flame,  but  at  the 
same  time  gives  the  miner  due  notice 
of  the  danger  which  he  was  running. 

With  the  complicated  improve- 
ments which  have  since  been  made 
in  the  Davy  lamp,  a  state  of  almost 


FIG.  32. — Gas  Jet  and  Davy  Lamp. 

absolute  safety  can  be  guaranteed,  but  still  from 
time  to  time  explosions  are  reported.  Of  the 
cause  of  many  we  are  absolutely  ignorant,  but 
occasionally  a  light  is  thrown  upon  their  origin 
by  a  paragraph  appearing  in  a  daily  paper.  Two 
men  are  charged  before  the  magistrates  with 
being  in  the  possession  of  keys  used  exclusively 
for  unlocking  their  miners'  safety-lamps.  There 
is  no  defence.  These  men  know  that  they  carry 
their  lives  in  their  hands,  yet  will  risk  their 
own  and  those  of  hundreds  of  others,  in  order 
that  they  may  be  able  to  light  their  pipes  by 
means  of  their  safety-lamps.  Sometimes  in  an 
unexpected  moment  there  is  a  great  dislodgment 


THE   COAL-MINE  AND   ITS   DANGERS.  93 

of  coal,  and  a  tremendous  quantity  of  gas  is  set 
free,  which  may  be  sufficient  to  foul  the  passages 
for  some  distance  around.  The  introduction  or 
exposure  of  a  naked  light  for  even  so  much  as  a 
second  is  sufficient  to  cause  explosion  of  the  mass ; 
doors  are  blown  down,  props  and  tubbing  are 
charred  up,  and  the  volume  of  smoke,  rushing  up 
by  the  nearest  shaft  and  overthrowing  the  engine- 
house  and  other  structures  at  the  mouth,  con- 
veys its  own  sad  message  to  those  at  the  surface,  of 
the  dreadful  catastrophe  that  has  happened  below. 
Perhaps  all  that  remains  of  some  of  the  workers 
consists  of  charred  and  scorched  bodies,  scarcely 
recognisable  as  human  beings.  Others  escape 
with  scorched  arms  or  legs,  and  singed  hair,  to 
tell  the  terrible  tale  to  those  who  were  more  for- 
tunately absent ;  to  speak  of  their  own  sufferings 
when,  after  having  escaped  the  worst  effects  of 
the  explosion,  they  encountered  the  asphyxiating 
rush  of  the  after-damp  or  choke-damp,  which 
had  been  caused  by  the  combustion  of  the  fire- 
damp. "  Choke-damp  "  in  very  truth  it  is,  for  it 
is  principally  composed  of  our  old  acquaintance 
carbonic  acid  gas  (carbon  dioxide),  which  is  well 
known  as  a  non-supporter  of  combustion,  and  as 
an  asphyxiator  of  animal  life. 

It  seems  a  terrible  thing  that  on  occasions  the 
workings  and  walls  themselves  of  the  coal-mine 
catch  fire  and  burn  incessantly.  Yet  such  is  the 
case.  Years  ago  this  happened  in  the  case  of  an 
old  colliery  near  Dudley,  at  the  surface  of  which, 
by  means  of  the  heat  and  steam  thus  afforded, 
early  potatoes  for  the  London  market,  we  are 
told,  were  grown ;  and  it  was  no  unusual  thing  to 
see  the  smoke  emerging  from  cracks  and  crevices 
in  the  rocks  in  the  vicinity  of  the  town. 


94 


THE   STORY   OF  A   PIECE   OF   COAL. 


From  fire  on  the  one  hand,  we  pass,  on  the 
other,  to  the  danger  which  awaits  miners  from  a 
sudden  inrush  of  water.  During  the  great  coal 
strike  of  1893,  certain  mines  became  unworkable 
in  consequence  of  the  quantity  of  water  which 
flooded  the  mines  and  which,  continually  passing 
along  the  natural  fractures  in  the  earth's  crust, 
is  always  ready  to  find  a  storage  reservoir  in  the 
workings  of  a  coal-mine.  This  is  a  difficulty 
which  is  always  experienced  in  the  sinking  of 
shafts,  and  the  shutting  off  of  water  engages 
the  best  efforts  of  mining  engineers. 

Added  to  these  various  dangers  which  exist  in 
the  coal-mine,  we  must  not  omit  to  notice  those 
accidents  that  are  continually  being  caused  by 
the  falling-in  of  roofs  or  of  walls,  from  the  falling 
of  insecure  timber,  or  of  what  are  known  as  "  coal- 
pipes  "  or  "bell-moulds."  Then,  again,  every 
man  that  enters  the  mine  trusts  his  life  to  the 
cage  by  which  he  descends  to  his  labour,  and 
shaft  accidents  are  not  infrequent. 


CAUSES  OF  DEATH. 

No.  of 
Deaths. 

Proportion 
per  cent. 

Deaths  resulting  from  fire-damp  ex- 
plosions   

2OIQ 

20.36 

Deaths  resulting  from  falling  roofs 
and  coals.  .  . 

OQCO 

3Q.87 

Deaths  resulting  from  shaft  acci- 
dents. .  

I7IO 

17.24 

Deaths  resulting  from  miscellaneous 
causes  and  above  ground  

2234. 

22.53 

9916 

lOO'OO 

The  above  table  shows  the  number  of  deaths 
from  colliery  accidents  in  England  for  ten  years, 


THE  COAL-MINE  AND   ITS  DANGERS.  95 


compiled  by  a  Government  inspector,  and  from 
this  it  will  be  seen  that  those  resulting  from  fall- 
ing roofs  number  considerably  more  than  one- 
,  third  of  the  whole. 

Every  reader  of  the  daily  papers  is  familiar 
with  the  harrowing  accounts  which  are  there 
given  of  coal-mine  explosions. 

This  kind  of  accident  is  one,  which  is,  above 
all,  associated  in  the  public  mind  with  the  dan- 
gers of  the  coal-pit.  Yet  the  accidents  arising 
from  this  cause  number  but  20  per  cent,  of  those 
recorded,  and  granted  there  be  proper  inspection, 
and  the  use  of  naked  lights  be  absolutely  abol- 
ished, this  low  per  centage  might  still  be  consider- 
[  ably  reduced. 

A  terrific  explosion  occurred  at  Whitwick  Col- 
liery, Leicestershire,  in  1893,  when  two  lads  were 
killed,  whilst  a  third  was  rescued  after  a  very 
narrow  escape.  The  lads,  it  is  stated,  were  work- 
ing with  naked  lights,  when  a  sudden  fall  of  coal 
released  a  quantity  of  gas,  and  an  immediate  ex- 
plosion was  the  natural  result.  Accidents  had 
been  so  rare  at  this  pit  that  it  was  regarded  as 
particularly  safe,  and  it  was  alleged  that  the  use 
of  naked  lights  was  not  uncommon. 

This  is  an  instance  of  that  large  number  of 
accidents  which  are  undoubtedly  preventable. 

An  interesting  commentary  on  the  careless 
manner  in  which  miners  risk  their  lives  was 
shown  in  the  discoveries  made  after  an  explosion 
at  a  colliery  near  Wrexham  in  1889.  Near  the 
scene  of  the  explosion  an  unsecured  safety-lamp 
was  found,  and  the  general  opinion  at  the  time 
was  that  the  disaster  was  caused  by  the  inex- 
cusable carelessness  of  one  of  the  twenty  vic- 
tims. Besides  this,  when  the  clothing  of  the 


96  THE  STORY  OF  A  PIECE  OF  COAL. 

bodies  recovered  was  searched,  the  contents, 
taken,  it  should  be  noted,  with  the  pitmen  into 
the  mines,  consisted  of  pipes,  tobacco,  matches, 
and  even  keys  for  unlocking  the  lamps.  It  is  a 
strange  reflection  on  the  manner  in  which  this 
mine  had  been  examined  previous  to  the  men  en- 
tering upon  their  work,  that  the  underlooker,  but 
half  an  hour  previously,  had  reported  the  pit  to 
be  free  from  gas. 

Another  instance  of  the  same  foolhardiness  on 
the  part  of  the  miners  is  contained  in  the  report 
issued  in  regard  to  an  explosion  which  occurred 
at  Denny,  in  Stirlingshire,  on  April  26th,  1895. 
By  this  accident  thirteen  men  lost  their  lives,  and 
upon  the  bodies  of  eight  of  the  number  the  fol- 
lowing articles  were  found  :  Upon  Patrick  Carr, 
tin  matchbox  half  full  of  matches  and  a  contri- 
vance for  opening  lamps  ;  John  Comrie,  split  nail 
for  opening  lamps;  Peter  Conway,  seven  matches 
and  split  key  for  opening  lamps  ;  Patrick  Dunton, 
split  nail  for  opening  lamps  ;  John  Herron,  clay 
pipe  and  piece  of  tobacco  ;  Henry  M'Govern,  tin 
matchbox  half  full  of  matches ;  Robert  Mitchell, 
clay  pipe  and  piece  of  tobacco ;  John  Nicol, 
wooden  pipe,  piece  of  tobacco,  one  match,  and 
box  half  full  of  matches.  The  report  stated  that 
the  immediate  cause  of  the  disaster  was  the  igni- 
tion of  fire-damp  by  naked  light,  the  conditions 
of  temperature  being  such  as  to  exclude  the  possi- 
bility of  spontaneous  combustion.  Henry  M'Gov- 
ern had  previously  been  convicted  of  having  a 
pipe  in  the  mine.  With  regard  to  the  question  of 
sufficient  ventilation  it  continued: — "  And  we  are 
therefore  le.d,  on  a  consideration  of  the  whole 
evidence,  to  the  conclusion  that  the  accident  can- 
not be  attributed  to  the  absence  of  ventilation, 


THE  COAL-MINE  AND   ITS   DANGERS.  97 

which  the  mine  owners  were  bound  under  the 
Mines  Regulation  Act  and  the  special  rules  to 
provide."  The  report  concluded  as  follows: — 
"  On  the  whole  matter  we  have  to  report  that,  in 
our  opinion,  the  explosion  at  Quarter  Pit  on 
April  26th,  1895,  resulting  in  the  loss  of  thirteen 
lives,  was  caused  by  the  ignition  of  an  accumula- 
tion or  an  outburst  of  gas  coming  in  contact  with 
a  naked  light,  '  other  than  an  open  safety-lamp/ 
which  had  been  unlawfully  kindled  by  one  of  the 
miners  who  were  killed.  In  our  opinion,  the  in- 
tensity of  the  explosion  was  aggravated,  and  its 
area  extended,  by  the  ignition  of  coal-dust." 

We  have  mentioned  that  accidents  have  fre- 
quently occurred  from  the  falling  of  "  coal-pipes," 
or,  as  they  are  also  called,  "  bell-moulds."  We 
must  explain  what  is  meant  by  this  term.  They 
are  simply  what  appear  to  be  solid  trunks  of 
trees  metamorphosed  into  coal.  If  we  go  into  a 
tropical  forest  we  find  that  the  woody  fibre  of 
dead  trees  almost  invariably  decays  faster  than 
the  bark  The  result  is  that  what  may  appear  to 
be  a  sound  tree  is  nothing  but  an  empty  cylinder 
of  bark.  This  appears  to  have  been  the  case 
with  many  of  the  trees  in  coal-mines,  where  they 
are  seen  to  pierce  the  strata,  and  around  which 
the  miners  are  excavating  the  coal.  As  the  coaly 
mass  collected  around  the  trunk  when  the  coal 
was  being  formed,  the  interior  was  undergoing  a 
process  of  decomposition,  while  the  bark  assumed 
the  form  of  coal.  The  hollow  interior  then  be- 
came filled  with  the  shale  or  sandstone  which 
forms  the  roof  of  the  coal,  and  its  sole  support 
when  the  coal  is  removed  from  around  it,  is  the 
thin  rind  of  carbonised  bark.  When  this  falls  to 
pieces,  or  loses  its  cohesion,  the  sandstone  trunk 
7 


98  THE   STORY  OF  A   PIECE  OF  COAL. 

falls  of  its  own  weight,  often  causing  the  death 
of  the  man  that  works  beneath  it.  Sir  Charles 

Lyell  mentions  that  in 
a  colliery  near  Newcas- 
tle, no  less  than  thirty 
sigillaria  trees  were 
standing  in  their  nat- 
ural position  in  an  area 
of  fifty  yards  square, 
the  interior  in  each; 
case  being  sandstone, 
which  was  surrounded 
by  a  bark  of  friable 
coal. 

The  last  great  dan- 
ger to  which  we  have 
here  to  make  reference, 
is  the  explosive  action 
of  a  quantity  of  coal- 
dust  in  a  dry  condition. 
It  is  only  now  com- 
mencing to  be  fully 
recognised  that  this  is 
really  a  most  dangerous 
FIG.  33.-Part  of  a  trunk  of  Sig-  explosive.  As  we  have 

illana,  showing  the  thin  out-  ,  .•*• 

er  carbonised  bark,  with  leaf-     seen>     lar£e     quantities 
scars,   and   the   seal-like   im-     of    COal    are    formed  al- 

remoled5  Where  the  bark  iS    most  exclusively  of  lep- 
idodendron    spores,   and 

such  coal  is  productive  of  a  great  quantity  of 
dust.  Explosions  which  are  always  more  or  less 
attributable  to  the  effects  of  coal-dust  are  gener- 
ally considered,  in  the  official  statistics,  to  have 
been  caused  by  fire-damp.  The  Act  regulating 
mines  in  Great  Britain  is  scarcely  up  to  date  in 
this  respect.  There  is  a  regulation  which  pro- 


THE   COAL-MINE   AND   ITS   DANGERS.  99 

i  vides  for  the  watering  of  all  dry  and  dusty  places 

>  within  twenty  yards  from  the  spot  where  a  shot 
is  fired,  but  the  enforcement  of  this  regulation  in 

^each  and  every  pit  necessarily  devolves  on  the 
managers,  many  of  whom  in  the  absence  of  an 

[inspector   leave   the   requirement  a  dead    letter. 

\  Every  improvement  which  results  in  the  better 
ventilation  of  a  coal-mine  tends  to  leave  the  dust 
in  a  more  dangerous  condition.  The  air,  as  it 
descends  the  shaft  and  permeates  the  workings, 

\  becomes  more  and  more  heated,  and  licks  up 
every  particle  of  moisture  it  can  touch.  Thor- 

:  ough  ventilation  results  in  more  greatly  freeing 
a  mine  of  the  dangerous  fire-damp,  but  the  remedy 
brings  about  another  disease,  viz.,  the  drying-up 

.of  all  moisture.  The  dust  is  thus  left  in  a  dan- 
gerously inflammable  condition,  acting  like  a 
train  of  gunpowder,  to  be  started,  it  may  be,  by 
the  slightest  breath  of  an  explosion.  There  is 
apparently  little  doubt  that  the  presence  of  coal- 
dust  in  a  dry  state  in  a  mine  appreciably  increases 
the  liability  of  explosion  in  that  mine. 

So  far  as  Great  Britain  is  concerned,  a  Royal 
Commission  was  appointed  by  Lord  Rosebery's 
Government  to  inquire  into  and  investigate  the 
facts  referring  to  coal-dust.  Generally  speaking, 
the  conclusion  arrived  at  was  that  fine  coal-dust 
was  inflammable  under  certain  conditions.  There 
was  considerable  difference  of  opinion  as  to  what 
these  conditions  were.  Some  were  of  opinion 
that  coal-dust  and  air  alone  were  of  an  explosive 
nature,  whilst  others  thought  that  alone  they  were 
not,  but  that  the  addition  of  a  small  quantity  of 
fire-damp  rendered  the  mixture  explosive.  An 
important  conclusion  was  come  to,  that,  with  the 
combustion  of  coal-dust  alone,  there  was  little  or 


100  THE  STORY  OF  A   PIECE  OF  COAL. 

no  concussion,  and  that  the  flame  was  not  of  an 
explosive  character. 

Coal-dust  was,  however,  admittedly  dangerous, 
especially  if  in  a  dry  condition.  The  effects  of 
an  explosion  of  gas  might  be  considerably  ex- 
tended by  its  presence,  and  there  seems  every 
reason  to  believe  that,  with  a  suitable  admixture 
of  air  and  a  very  small  proportion  of  gas,  it  forms 
a  dangerous  explosive.  Legislation  in  the  direc- 
tion of  the  report  of  the  Commission  is  urgently 
needed. 

We  have  seen  elsewhere  what  it  is  in  the  dust 
which  makes  it  dangerous,  how  that,  for  the  most 
part,  it  consists  of  the  dust-like  spores  of  the 
lepidodendron  tree,  fine  and  impalpable  as  the 
spores  on  the  backs  of  some  of  our  living  ferns, 
and  the  fact  that  this  consists  of  a  large  propor- 
tion of  resin  makes  it  the  easily  inflammable  sub- 
stance it  is.  No  explosion  in  the  anthracite 
region  of  Pennsylvania  has  ever  been  traced  with 
certainty  to  coal-dust,  and  it  is  only  in  very  dry 
mines  that  bituminous  dust  can  be  explosive.  In 
1888,  however,  there  was  an  explosion  of  coal- 
dust  in  a  bituminous  coal-mine  at  Pittsburg,  Kan., 
by  which  over  a  hundred  lives  were  lost. 

In  some  of  the  pits  in  South  Wales  a  system 
of  fine  sprays  of  water  is  in  use,  by  which  the 
water  is  ejected  from  pin-holes  pricked  in  a  series 
of  pipes  which  are  carried  through  the  workings. 
A  fine  mist  is  thus  caused  where  necessary,  which 
is  carried  forward  by  the  force  of  the  ventilating 
current. 

A  thorough  system  of  inspection  in  coal- 
mines throughout  the  world  is  undoubtedly 
urgently  called  for,  in  order  to  ensure  the  proper 
carrying  out  of  the  various  regulations  framed  for 


EARLY   HISTORY-ITS   USE  AND   ITS  ABUSE.   IOI 

their  safety.  It  is  extremely  unfortunate  that  so 
many  of  the  accidents  which  happen  are  pre- 
ventable, if  only  men  of  knowledge  and  of  scien- 
tific attainments  filled  the  responsible  positions 
of  the  overlookers. 


CHAPTER  V. 

EARLY    HISTORY — ITS    USE    AND    ITS    ABUSE. 

THE  extensive  use  of  coal  throughout  the 
civilised  world  for  purposes  of  heating  and  illumi- 
nation, and  for  the  carrying  on  of  manufactures 
and  industries,  may  be  regarded  as  a  well-marked 
characteristic  of  the  age  in  which  we  live^ 

Coal  must  have  been  in  centuries  past  a 
familiar  object  to  many  generations.  People 
must  have  long  been  living  in  close  proximity  to 
its  outcrops  at  the  sides  of  the  mountains  and  at 
the  surface  of  the  land,  yet  without  being  ac- 
quainted with  its  practical  value,  and  it  seems 
strange  that  so  little  use  was  made  of  it  until 
about  three  centuries  ago,  and  that  its  use  did 
not  spread  earlier  and  more  quickly  throughout 
civilised  countries. 

A  mineral  fuel  is  mentioned  by  Theophrastus 
about  300  B.  c.,  from  which  it  is  inferred  that 
thus  early  it  was  dug  from  some  of  the  more 
shallow  depths.  The  Britons  before  the  time  of 
the  Roman  invasion  are  credited  with  some 
slight  knowledge  of  its  industrial  value.  Pre- 
historic excavations  have  been  found  in  Mon- 
mouthshire, and  at  Stanley,  in  Derbyshire,  and 
the  flint  axes  there  actually  found  imbedded  in 


102  THE   STORY  OF  A   PIECE   OF   COAL. 

the  layer  of  coal  are  reasonably  held  to  indicate 
its  excavation  by  neolithic  or  palaeolithic  (stone- 
age)  workmen. 

The  fact  that  coal  cinders  have  been  found  on 
old  Roman  walls  in  conjunction  with  Roman 
tools  and  implements,  goes  to  prove  that  its  use, 
at  least  for  heating  purposes,  was  known  in  Eng- 
land prior  to  the  Saxon  invasion,  whilst  some 
polygonal  chambers  in  the  six-foot  seam  near 
the  river  Douglas,  in  Lancashire,  are  supposed 
also  to  be  Roman. 

The  Chinese  were  early  acquainted  with  the 
!  existence  of  coal,  and  knew  of  its  industrial 
value  to  the  extent  of  using  it  for  the  baking  of 
porcelain. 

The  fact  of  its  extensive  existence  in  Great 
Britain,  and  the  valuable  uses  to  which  it  might 
be  put,  did  not,  however,  meet  with  much  notice 
until  the  ninth  century,  when,  owing  to  the  de- 
crease of  the  forest-area,  and  consequently  of  the 
supply  of  wood-charcoal  therefrom,  it  began  to 
attract  attention  as  affording  an  excellent  substi- 
tute for  charcoal. 

The  coal-miner  was,  however,  still  a  creation 
of  the  future,  and  even  as  peat  is  collected  in  Ire- 
land at  the  present  day  for  fuel,  without  the  la- 
borious process  of  mining  for  it,  so  those  people 
living  in  coal-bearing  districts  found  their  needs 
satisfied  by  the  quantity  of  coal,  small  as  it  was, 
which  appeared  ready  to  hand  on  the  sides  of  the 
carboniferous  mountains.  Till  then,  and  for  a 
long  time  afterwards,  the  principal  source  of  fuel 
consisted  of  vast  forests,  amidst  which  the  char- 
coal-burners, or  "  colliers  "  as  they  were  even  then 
called,  lived  out  their  lonely  existence  in  preparing 
charcoal  and  hewing  wood,  for  the  fires  of  the 


EARLY  HISTORY— ITS   USE  AND   ITS  ABUSE.   103 


aronial  halls  and  stately  castles  then  swarming 
throughout  the  land.  As  the  forests  became  used 
up,  recourse  was  had  more  and  more  to  coal,  and 
in  1239  the  first  charter  dealing  with  and  recognis- 
ing the  importance  of  the  supplies  was  granted 
to  the  freemen  of  Newcastle,  according  them 
permission  to  dig  for  coals  in  the  Castle  fields. 
About  the  same  time  a  coal-pit  at  Preston,  Had- 
dingtonshire,  was  granted  to  the  monks  of  New- 
battle. 

Specimens  of  Newcastle  coal  were  sent  to 
London,  but  the  city  was  loth  to  adopt  its  use, 
objecting  to  the  innovation  as  one  prejudicial 
to  the  health  of  its  citizens.  By  the  end  of  the 
i6th  century,  two  ships  only  were  found  sufficient 
to  satisfy  the  demand  for  stone-coal  in  London. 
This  slow  progress  may,  perhaps,  have  been  par- 
tially owing  to  the  difficulties  which  were  placed 
in  the  way  of  its  universal  use.  Great  opposition 
was  experienced  by  those  who  imported  it  into 
the  metropolis,  and  the  increasing  amount  which 
was  used  by  brewers  and  others  about  the  year 
1300,  caused  serious  complaints  to  be  made,  the 
effect  of  which  was  to  induce  Parliament  to  obtain 
a  proclamation  from  the  King  prohibiting  its  use, 
and  empowering  the  justices  to  inflict  a  fine  on 
those  who  persisted  in  burning  it.  The  nuisance 
which  coal  has  since  proved  itself,  in  England  by 
polluting  the  atmosphere  and  by  denuding  wide 
tracts  of  country  of  all  vegetation,  was  even  thus 
early  recognised,  and  had  the  efforts  which  were 
then  made  to  stamp  out  its  use,  proved  successful, 
those  who  live  now  in  the  great  cities  might  never 
have  become  acquainted  with  that  species  of 
black  winter  fog  which  at  times  hangs  like  a  pall 
over  them,  and  transforms  the  brightness  of  day 


104  THE   STORY   OF   A   PIECE   OF   COAL. 

into  a  darkness  little  removed  from  that  of  night. 
At  the  same  time,  we  must  bear  in  mind  that  it  is 
universally  acknowledged  that  England  owes  her ' 
prosperity,  and  her  pre-eminence  in  commerce,  in 
great  part,  to  her  happy  possession  of  wide  and 
valuable  coal-fields,  and  many  authorities  have 
not  hesitated  to  say,  that,  in  their  opinion,  the 
length  of  time  during  which  England  will  con- 
tinue to  hold  her  prominent  position  as  an  in- 
dustrial nation  is  limited  by  the  time  during  which 
her  coal  will  last. 

The  attempt  to  prohibit  the  burning  of  coal 
was  not,  however,  very  successful,  for  in  the^ 
reign  of  Edward  III.  a  license  was  again  granted 
to  the  freemen  of  Newcastle  to  dig  for  coals. 
Newcastle  was  thus  the  first  town  to  become 
famous  as  the  home  of  the  coal-miner,  and  the 
fame  which  it  early  acquired,  it  has  held  unceas- 
ingly ever  since. 

Other  attempts  at  prohibition  of  the  article 
were  made  at  various  times  subsequently,  amongst 
them  being  one  which  was  made  in  Elizabeth's 
reign.  It  was  supposed  that  the  health  of  the 
country  squires,  who  came  to  town  to  attend  the 
session  of  Parliament,  suffered  considerably  dur- 
ing their  sojourn  in  London,  and,  to  remedy  this 
serious  state  of  affairs,  the  use  of  stone-coal  dur- 
ing the  time  Parliament  was  sitting  was  once  more 
prohibited. 

Coal  was,  however,  by  this  time  beginning  to 
be  recognised  as  a  most  valuable  and  useful 
article  of  fuel,  and  had  taken  a  position  in  the 
industrial  life  of  the  country  from  which  it  was 
difficult  to  remove  it.  Rather  than  attempt  to 
have  arrested  the  growing  use  of  coal,  Parlia- 
ment would  have  been  better  employed  had  it 


EARLY   HISTORY— ITS   USE  AND   ITS  ABUSE.   105 

framed  laws  compelling  the  manufacturers  and 
other  large  burners  to  consume  their  own  smoke, 
and  instead  of  aiming  at  total  prohibition,  have 
encouraged  an  intelligent  and  more  economical 
use  of  it. 

In  spite  of  all  prohibition  its  use  rapidly 
spread,  and  it  was  soon  applied  to  the  smelting 
of  iron  and  to  other  purposes.  Iron  had  been 
largely  produced  in  the  south  of  England  from 
strata  of  the  Wealden  formation,  during  the  ex- 
istence of  the  great  forest  which  at  one  time  ex- 
tended for  miles  throughout  Surrey  and  Sussex. 
The  discovery  of  coal,  however,  and  the  opening 
up  of  many  mines  in  the  north,  gave  an  important 
impetus  to  the  smelting  of  iron  in  those  counties, 
and  as  the  forests  of  the  Weald  became  exhausted, 
the  iron  trade  gradually  declined.  Furnace  after 
furnace  became  extinguished,  until  in  1809  that 
at  Ashburnham,  which  had  lingered  on  for  some 
years,  was  compelled  to  bow  to  the  inevitable 
fate  which  had  overtaken  the  rest  of  the  iron 
blast-furnaces. 

Bituminous  coa^was  mined  in  Virginia  about 
1750  and  around  CPjttsbufg,  Pa),  before  1760. 
Pittsburg  coal  was  in  general  use  in  the  region 
round  about  the  mines  at  the  beginning  of  the 
nineteenth  century  both  for  manufacturing  and 
household  purposes,  and  shipments  to  Philadelphia 
soon  began.  Much  difficulty  was  met  with  in 
bringing  anthracite  into  use  in  America.  It  was 
discovered  near  Wilkes  Barre  in  1762,  but  being 
much  harder  than  the  kind  they  had  known  in 
England  the  colonists  were  unable  to  make  it 
burn.  It  was  first  successfully  used  in  black- 
smiths' forges,  with  the  aid  of  the  bellows,  and 
was  employed  in  the  Pennsylvania  armory  at 


Io6  THE  STORY  OF  A   PIECE  OF  COAL. 

Carlisle  in  the  manufacture  of  firearms  for  the 
Continental  troops  during  the  Revolution.  Coal 
was  found  also  in  other  parts  of  the  anthracite 
region  between  1790  and  1826.  Each  of  the 
earlier  mine-owners  in  turn  tried  to  make  a 
market  for  the  mineral  in  Philadelphia,  but  all 
met  with  failure  until  they  introduced  specially 
adapted  grates  and  their  customers  learned,  gen- 
erally by  accident,  that  an  anthracite  fire  must 
not  be  poked  incessantly.  But  progress  was  still 
slow,  so  that  in  1820  the  365  tons  sent  from  the 
Lehigh  region  were  enough  to  supply  the  market. 
In  1831,  however,  the  shipments  from  this  district 
had  advanced  to  40,000  tons,  and  in  1892  to  nearly 
6,500,000. 

Anthracite  coal  is  practically  free  from  the  iron 
pyrites  which  gives  off  the  sulphurous  fumes  so 
much  complained  of  in  England,  and  the  little 
smoke  yielded  by  American  anthracite  readily 
passes  away  in  the  drier  air  of  this  country. 

In  his  interesting  work,  "  Sylvia,"  published 
in  1661,  ffivelyn)  in  speaking  of  the  noxious 
vapours  pourecTout  into  the  air  by  the  increas- 
ing number  of  coal  fires,  writes,  "  This  is  that 
pernicious  smoke  which  sullies  all  her  glory, 
superinducing  a  sooty  crust  or  furr  upon  all  that 
it  lights,  spoiling  movables,  tarnishing  the  plate, 
gildings  and  furniture,  and  corroding  the  very 
iron  bars  and  hardest  stones  with  those  piercing 
and  acrimonious  spirits  which  accompany  its 
sulphur,  and  executing  more  in  one  year  than 
•  the  pure  air  of  the  country  could  effect  in  some 
hundreds."  The  evils  here  mentioned  are  those 
which  have  grown  and  have  become  intensified 
a  hundred-fold  during  the  two  centuries  and  a 
half  which  have  since  elapsed.  When  the  many 


EARLY  HISTORY— ITS  USE  AND  ITS  ABUSE.  107 

efforts  which  were  made  to  limit  its  use  in  the 
'•  years  prior  to  1600  are  remembered;  at  which 
time,  we  are  informed,  two  ships  only  were  engaged 
in  bringing  coal  to  London,  it  at  once  appears 
how  paltry  are  the  efforts  made  now  to  moderate 
these  same  baneful  influences  on  the  atmosphere, 
at  a  time  when  the  annual  consumption  of  coal 
in  the  United  Kingdom  has  reached  the  enormous 
total  of  190  millions  of  tons.  The  various  smoke- 
abatement  associations  which  have  started  into 
existence  during  the  last  few  years  are  doing 
a  little,  although  very  little,  towards  directing 
popular  attention  to  the  subject;  but  there  is  an 
enormous  task  before  them,  that  of  awakening 
every  individual  to  an  appreciation  of  the  per- 
sonal interest  which  he  has  in  their  success,  and 
to  realise  how  much  might  at  once  be  done  if 
each  were  to  do  his  share,  minute  though  it  might 
be,  towards  mitigating  the  evils  of  the  present 
mode  of  coal-consumption.  Probably  very  few 
householders  ever  realise  what  important  factors 
their  chimneys  constitute,  in  bringing  about  air 
pollution,  and  the  more  they  do  away  with  the 
use  of  bituminous  coal  for  fuel,  the  nearer  they 
will  be  to  the  time  when  the  English  yellow  fog 
will  be  a  thing  of  the  past. 

A  large  proportion  of  smoke  consists  of  parti- 
cles of  pure  unconsumed  carbon,  and  this  is  ac- 
/  companied  by  sulphurous  acid,  begotten  by  the 
sulphur  which  is  contained  in  the  coal  ordinarily 
used  in  England  to  the  amount  of  about  eight 
pounds  in  every  thousand ;  by  sulphuretted  hy- 
drogen, by  hydro-carbons,  and  by  vapours  of 
various  kinds  of  oils,  small  quantities  of  ammonia, 
and  other  bodies  not  by  any  means  contributing 
to  a  healthy  condition  of  the  atmosphere.  A 


108  THE   STORY  OF  A   PIECE   OF   COAL. 

good  deal  of  the  heavier  carbon  is  deposited 
along  the  walls  of  chimneys  in  the  form  of  soot, 
together  with  a  small  percentage  of  sulphur  of 
ammonia  ;  this  is  as  a  consequence  very  generally 
used  for  manure.  The  remainder  is  poured  out 
into  the  atmosphere,  there  to  undergo  fresh 
changes,  and  to  become  a  fruitful  cause  of  those 
thick  black  fogs  with  which  town-dwellers  are  so 
familiar.  Sulphuretted  hydrogen  (H2S)  is  a  gas 
well  known  to  students  of  chemistry  as  a  most 
powerful  reagent,  its  most  characteristic  external 
property  being  the  extremely  offensive  odour 
which  it  possesses,  and  which  bears  a  strong 
resemblance  to  that  of  rotten  eggs  or  decompos- 
ing fish.  It  tarnishes  silver  work  and  picture 
frames  very  rapidly.  On  combustion  it  changes 
to  sulphurous  acid  (SO2),  and  this  in  turn  has 
the  power  of  taking  up  from  the  air  another 
atom  of  oxygen,  forming  sulphuric  acid  (SO3  -f- 
water),  or,  as  we  more  familiarly  know  it,  oil  of 
vitriol. 

Yet  the  smoke  itself,  including  as  it  does  all 
the  many  impurities  which  exist  in  coal,  is  not 
only  evil  in  itself,  but  is  evil  in  its  influences.  Dr. 
Siemens  has  said  : — "  It  has  been  shown  that  the 
fine  dust  resulting  from  the  imperfect  combustion 
of  coal  was  mainly  instrumental  in  the  formation 
of  fog;  each  particle  of  solid  matter  attracting 
to  itself  aqueous  vapour.  These  globules  of  fog 
were  rendered  particularly  tenacious  and  dis- 
agreeable by  the  presence  of  tar  vapour,  another 
result  of  imperfect  combustion  of  raw  fuel,  which 
might  be  turned  to  better  account  at  the  dye- 
works.  The  hurtful  influence  of  smoke  upon 
public  health,  the  great  personal  discomfort  to 
which  it  gave  rise,  and  the  vast  expense  it 


EARLY   HISTORY— ITS   USE  AND   ITS  ABUSE.   109 

indirectly  caused  through  the  destruction  of  our 
monuments,  pictures,  furniture,  and  apparel,  were 
now  being  recognised." 

The  most  effectual  remedy  would  result  from 
a  general  recognition  of  the  fact  that  wherever 
smoke  was  produced,  fuel  was  being  consumed 
wastefully,  and  that  all  our  calorific  effects,  from 
the  largest  furnace  to  the  domestic  fire,  could  be 
realised  as  completely,  and  more  economically, 
without  allowing  any  of  the  fuel  employed  to  reach 
the  atmosphere  unburnt.  This  most  desirable 
result  might  be  effected  by  the  use  of  gas  for  all 
heating  purposes,  with  or  without  the  additional 
use  of  coke  or  anthracite.  The  success  of  the  so- 
called  smoke-consuming  stoves  is  greatly  open  to 
question,  whilst  some  of  them  have  been  reported 
upon  by  those  appointed  to  inspect  them  as  ac- 
tually accentuating  the  incomplete  combustion, 
the  abolition  of  which  they  were  invented  to  bring 
about. 

The  smoke  nuisance  is  one  which  cuts  at  the' 
very  basis  of  business  life  where  it  prevails.  The 
cloud  which,  under  certain  atmospheric  condi- 
tions, rests  like  a  pall  over  the  great  cities  of 
England  and  the  central  United  States,  will  not 
•even  permit  at  times  of  a  single  ray  of  sunshine 
permeating  it.  No  one  knows  at  what  hour  to 
expect  it.  It  is  like  a  giant  spectre  which,  hav- 
ing lain  dormant  since  the  carboniferous  age,  has 
been  raised  into  life  and  being  at  the  call  of  rest- 
less humanity ;  it  is  now  punishing  those  who 
have  summoned  it  to  their  service  by  clasping 
them  in  its  deadly  arms,  cutting  off  the  brilliant 
sunshine,  and  necessitating  the  use  in  the  day- 
time of  artificial  light;  inducing  all  kinds  of  bron- 
chial and  throat  affections,  corroding  telegraph 


110  THE   STORY  OF  A   PIECE  OF   COAL. 

and    telephone    wires,   and  weathering  away   the 
masonry  of  public  buildings. 

The  immense  value  to  us  of  the  coal-deposits 
which  lie  buried  in  such  profusion  in  the  earth 
beneath  us,  can  only  be  appreciated  when  we  con- 
sider the  many  uses  to  which  coal  has  been  put. 
We  must  remember,  as  we  watch  the  ever-ex- 
tending railway  ramifying  the  country  in  every 
direction,  that  the  first  railway  and  the  first 
locomotive  ever  built,  were  those  which  were 
brought  into  being  in  1814  by  George  Stephen- 
son,  for  the  purpose  of  the  carriage  of  coals  from 
the  Killingworth  Colliery.  To  the  importance  of 
coal  in  our  manufactures,  therefore,  we  owe  the 
subsequent  development  of  steam  locomotive 
power  as  the  means  of  the  introduction  of 
passenger  traffic,  and  by  the  use  of  coal  we  are 
enabled  to  travel  from  one  end  of  the  country  to 
the  other  in  a  space  of  time  inconceivably  small 
as  compared  with  that  occupied  on  the  same 
journey  in  the  old  coaching  days.  The  increased 
rapidity  with  which  our  vessels  cross  the  wide 
ocean  we  owe  to  the  use  of  coal ;  our  mines  are 
carried  to  greater  depths  owing  to  the  power  our 
pumping-engines  obtain  from  coal  in  clearing 
the  mines  of  water  and  in  ensuring  ventilation  ; 
the  enormous  development  of  the  iron  trade  only ' 
became  possible  with  the  increased  blast  power 
obtained  from  the  consumption  of  coal,  and  the 
very  hulls  and  engines  of  our  steamships  are 
made  of  this  iron  ;  our  railroads  and  engines  are 
mostly  of  iron,  and  when  we  think  of  the  exten- 
sive use  of  iron  utensils  in  every  walk  of  life,  we 
see  how  important  becomes  the  powrer  we  possess 
of  obtaining  the  necessary  fuel  to  feed  the  smelt- 
ing furnaces.  Evaporation  by  the  sun  was  at 


HOW  GAS   IS   MADE,    ETC. 


me  time  the  sole  means  of  obtaining  salt  from 
sea-water ;  now  coal  is  used  to  boil  the  salt  pans 
and  to  purify  the  brine  from  the  salt-mines  of 
Michigan  or  New  York.  The  extent  to  which 
gas  is  used  for  illuminating  purposes  reminds  us 
of  another  important  product  obtained  from 
coal.  Paraffin^LajidLpetioleum  may  be  obtained 
from  it,  whilst  candles,  oils,  dyes,  lubricants,  and 
many  other  useful  articles  go  to  attest  the  impor- 
tance of  the  underground  stores  of  that  mineral 
which  has  well  and  deservedly  been  termed  the 
"  black  diamond." 


CHAPTER  VI. 

HOW     GAS     IS     MADE — ILLUMINATING     OILS     AND 
BYE-PRODUCTS. 

ACCUSTOMED  as  we  are  at  the  present  day  to 
see  street  after  street  of  well-lighted  thorough- 
fares, brilliantly  illuminated  by  gas-lamps  main- 
tained by  public  authority,  we  can  scarcely  appre- 
ciate the  fact  that  the  use  of  gas  is,  comparatively 
speaking,  of  but  recent  growth,  and  that,  like 
the  use  of  coal  itself,  it  has  not  yet  existed  a 
century  in  public  favour.  Valuable  as  coal  is 
in  very  many  different  ways,  perhaps  next  in 
value  to  its  actual  use  as  fuel,  ranks  the  use  of 
the  immediate  product  of  its  distillation" — viz., 
gas  ;  and  although  gas  is  in  some  respects  wan- 
ing before  the  march  of  the  electric  light  in  our 
day,  yet,  even  as  gas  at  no  time  has  altogether 
superseded  old-fashioned  oil,  so  we  need  not 


112  THE  STORY   OF   A  PIECE  OF  COAL. 

anticipate  a  time  when  gas  in  turn  will  be  likely 
to  be  superseded  by  the  electric  light,  there 
being  many  uses  to  which  the  one  may  be  put,  to 
which  the  latter  would  be  altogether  inapplicable  ; 
for,  in  the  words  of  Dr.  Siemens,  assuming  the 
cost  of  electric  light  to  be  practically  the  same- 
as  gas,  the  preference  for  one  or  other  would  in 
each  application  be  decided  upon  grounds  of  rela- 
tive convenience,  but  gas-lighting  would  hold  its 
own  as  the  poor  man's  friend.  Gas  is  an  institu- 
tion of  the  utmost  value  to  the  artisan  ;  it  re- 
quires hardly  any  attention,  is  supplied  upon 
regulated  terms,  and  gives,  with  what  should  be  a 
cheerful  light,  a  genial  warmth,  which  often  saves 
the  lighting  of  a  fire. 

The  revolution  which  gas  has  made  in  the  ap- 
pearance of  the  streets,  where  formerly  the  only 
illumination  was  that  provided  by  each  house- 
holder, who,  according  to  his  means,  hung  out  a 
more  or  less  efficient  lantern,  and  consequently  a 
more  or  less  smoky  one,  cannot  fail  also  to  have 
brought  about  a  revolution  in  the  social  aspects 
of  the  streets,  and  therefore  is  worthy  to  be 
ranked  as  a  social  reforming  agent ;  and  some 
slight  knowledge  of  the  process  of  its  manufac- 
ture, such  as  it  is  here  proposed  to  give,  should 
be  in  the  possession  of  every  educated  individual. 
Yet  the  subjects  which  must  be  dealt  with  in  this 
chapter  are  so  numerous  and  of  such  general  in- 
terest, that  we  shall  be  unable  to  enter  more  than 
superficially  into  any  one  part  of  the  whole,  but 
shall  strive  to  give  a  clear  and  comprehensive 
view,  which  shall  satisfy  the  inquirer  who  is  not  a 
specialist. 

The  credit  of  the  first  attempt  at  utilising  the 
gaseous  product  of  coal  for  illumination  appears 


HOW  GAS   IS  MADE,   ETC.  113 


£  to  be  due  to  Murdock,  an  engineer  at  Redruth, 
who,  in  1792,  introduced  it  into  his  house  and 
offices,  and  who,  ten  years  afterwards,  as  the  re- 
sult of  numerous  experiments  which  he  made 
with  a  view  to  its  utilisation,  made  a  public  dis- 
play at  Birmingham  on  the  occasion  of  the  Peace 
of  Amiens,  in  1802. 

More  than  a  century  before,  however,  the  gas 
obtained  from  coal  had  been  experimented  upon 
by  a  Dr.  Clayton,  who,  about  1690,  conceived  the 
idea  of  heating  coal  until  its  gaseous  constituents 
were  forced  out  of  it.  He  described  how  he  ob- 
tained steam  first  of  all,  then  a  black  oil,  and 
finally  a  u  spirit,"  as  our  ancestors  were  wont  to 
term  the  gas.  This,  to  his  surprise,  ignited  on  a 
light  being  applied  to  it,  and  he  considerably 
amused  his  friends  with  the  wonders  of  this  in- 
flammatory spirit.  For  a  century  afterwards  it 
remained  in  its  early  condition,  a  chemical  won- 
der, a  thing  to  be  amused  with  ;  but  it  required 
the  true  genius  and  energy  of  Murdock  to  show 
the  great  things  of  which  it  was  capable. 

London  received  its  first  instalment  of  gas  in 
1807,  and  during  the  next  few  years  its  use  be- 
came more  and  more  extended,  houses  and  streets 
rapidly  receiving  supplies  in  quick  succession.  It 
was  not,  however,  till  about  the  year  1820  that  its 
use  throughout  the  country  became  at  all  gen- 
eral, St.  James'  Park  being  gas-lit  in  the  succeed- 
ing year.  Little  more  than  eighty  years  ago, 
and  amongst  the  many  wonderful  things  which 
sprung  up  during  the  nineteenth  century,  perhaps 
we  may  place  in  the  foremost  rank  for  actual 
utility,  the  gas  extracted  from  coal,  conveyed  as 
it  is  through  miles  upon  miles  of  underground 
pipes  into  the  very  homes  of  the  people,  and  con- 
8 


114 


THE   STORY   OF   A   PIECE   OF   COAL. 


stituting   now  almost   as  much  a  necessity   of  a 
comfortable  existence  as  water  itself. 


FIG.  34. — Inside  a  Gas-Holder. 

The  use  of  gas  thus  rapidly  extended  for  illu- 
minating purposes,  and   to  a  very  great  extent 


HOW   GAS   IS   MADE,    ETC.  115 

superseded  the  old-fashioned  means  of  illumina- 
tion. 

The  gas  companies  which  sprang  up  were  not 
slow  to  notice  that,  seeing  the  gas  was  supplied 
by  meter,  it  was  to  their  pecuniary  advantage  "  to 
give  merely  the  prescribed  illuminating  power, 
and  to  discourage  the  invention  of  economical 
burners,  in  order  that  the  consumption  might 
reach  a  maximum.  The  application  of  gas  for 
heating  purposes  had  not  been  encouraged,  and 
was  still  made  difficult  in  consequence  of  the  ob- 
jectionable practice  of  reducing  the  pressure  in 
the  mains  during  daytime  to  the  lowest  possible 
point  consistent  with  prevention  of  atmospheric 
indraught." 

The  introduction  of  an  important  rival  into 
the  field  in  the  shape  of  the  electric  light  has  now 
given  a  powerful  impetus  to  the  invention  and 
introduction  of  effective  gas-lamps,  and  various 
appliances  for  effecting  savings  in  the  amount  of 
gas  consumed  or  giving  greater  efficiency  are 
now  widely  advertised.  As  long  as  gas  retained 
almost  the  monopoly,  there  was  no  incentive  to 
the  gas  companies  to  produce  an  effective  light 
cheaply ;  but  now  that  the  question  of  the  rela- 
tive cheapness  of  gas  and  electricity  is  being 
actively  discussed,  the  gas  companies,  true  to  the 
instinct  of  self-preservation,  seem  determined  to 
show  what  can  be  done  when  gas  is  consumed  in 
a  scientific  manner. 

In  order  to  understand  how  best  a  burner 
should  be  constructed  in  order  that  the  gas  that 
is  burnt  should  give  the  greatest  possible  amount 
of  illumination,  let  us  consider  for  a  moment  the 
composition  of  the  gas  flame.  It  consists  of 
three  parts,  (i)  an  interior  dark  space,  in  which 


Il6  THE  STORY  OF  A  PIECE  OF  COAL. 

the  elements  of  the  gas  are  in  an  unconsumed 
state  ;  (2)  an  inner  ring  around  the  former,  whence 
the  greatest  amount  of  light  is  obtained,  and  in 
which  are  numerous  particles  of  carbon  at  a  white 
heat,  each  awaiting  a  supply  of  oxygen  in  order 
to  bring  about  combustion  ;  and  (3)  an  outer  ring 
of  blue  flame  in  which  complete  combustion  has 
taken  place,  and  from  which  the  largest  amount 
of  heat  is  evolved. 

The  second  of  these  portions  of  the  flame  cor- 
responds with  the  "  reducing"  flame  of  the  blow- 
pipe, since  this  part,  ifTurned  upon  an  oxide,  will 
reduce  it,  i.  e.,  abstract  its  oxygen  from  it.  This 
part  also  corresponds  with  the  jet  of  the  Bunsen 
burner,  when  the  holes  are  closed  by  which  other- 
wise air  would  mingle  with  the  gas,  or  with  the 
flame  from  a  gas-stove  when  the  gas  ignites  be- 
neath the  proper  igniting-jets,  and*  which  gives 
consequently  a  white  or  yellow  flame. 

The  third  portion,  on  the  other  hand,  corre- 
sponds with  the  "oxidising"  flame  of  the  blow- 
pipe, since  it  gives  up  oxygen  to  bodies  that  are 
thirsting  for  it.  This  also  corresponds  with  the 
ordinary  blue  flame  of  the  Bunsen  burner,  and 
with  the  blue  flame  of  gas-stoves  where  heat,  and 
not  light,  is  required,  the  blue  flame  in  both 
cases  being  caused  by  the  admixture  of  air  with 
the  gas. 

Thus,  in  order  that  gas  may  give  the  best 
illumination,  we  must  increase  the  yellow  or  white 
space  of  carbon  particles  at  a  white  heat,  and  a 
burner  that  will  do  this,  and  at  the  same  time 
hold  the  balance  so  that  unconsumed  particles  of 
carbon  shall  not  escape  in  the  way  of  smoke,  will 
give  the  most  successful  illuminating  results. 
With  this  end  in  view  the  addition  of  albo-carbon 


HOW  GAS   IS  MADE,   ETC.  117 

to  a  bulb  in  the  gas-pipe  has  proved  very  success- 
ful, and  the  incandescent  gas-jet  is  constructed 
on  exactly  the  same  chemical  principle.  The  in- 
vention of  burners  which  brought  about  this  de- 
sirable end  has  doubtless  not  been  without  effect 
in  acting  as  a  powerful  obstacle  to  the  wide- 
spread introduction  of  the  electric  light. 

Without  entering  into  details  of  the  manufac- 
ture of  gas,  it  will  be  as  well  just  to  glance  at 
the  principal. parts  of  the  apparatus  used. 

The  gasometer,  as  it  has  erroneously  been 
called,  is  a  familiar  object  to  most  people,  not 
only  to  sight,  but  unfortunately  also  to  the  organs 
of  smell.  It  is  in  reality  of  course  only  the  gas- 
holder, in  which  the  final  product  of  distillation 
of  the  coal  is  stored,  and  from  which  the  gas  im- 
mediately passes  into  the  distributing  mains. 

The  first,  and  perhaps  most  important,  portion 
of  the  apparatus  used  in  gas-making,  is  the  series 
of  retorts  into  which  the  coal  is  placed,  and  from 
which,  by  the  application  of  heat,  the  various 
volatile  products  distil  over.  These  retorts  are 
huge  cast-iron  vessels,  encased  in  strong  brick- 
work, usually  five  in  a  group,  and  beneath  which 
a  large  furnace  is  kept  going  until  the  process  is 
complete.  Each  retort  has  an  iron  exit  pipe 
affixed  to  it,  through  which  the  gases  generated 
by  the  furnace  are  carried  off.  The  exit  pipes 
all  empty  themselves  into  what  is  known  as  the 
hydraulic  main,  a  long  horizontal  cylinder,  and  in 
this  the  gas  begins  to  deposit  a  portion  of  its 
impurities.  The  immediate  products  of  distilla- 
tion are,  after  steam  and  air,  gas,  tar,  ammoniacal 
liquor,  sulphur  in  various  forms,  and  coke,  the 
last  being  left  behind  in  the  retort.  In  the  hy- 
draulic main  some  of  the  tar  and  ammoniacal 


Il8          THE   STORY  OF   A   PIECE   OF   COAL. 

liquor  already  begin   to  be  deposited.     The  gas 
passes  on   to   the  £vnd£ns££»which   consists  of  a 


FIG.  35.— Filling  Retorts  by  Machinery. 

number  of  U-shaped  pipes.  Here  the  impurities 
are  still  further  condensed  out,  and  are  collected 
in  the  tar-pit  whilst  the  gas  proceeds,  still  further 
lightened  of  its  impurities.  It  may  be  mentioned 


HOW  GAS  IS   MADE,   ETC.  119 

that  the  temperature  of  the  gas  in  the  condenser 
is  reduced  to  about  60°  F.,  but  below  this  some 
of  the  most  valuable  of  the  illuminants  of  coal- 
gas  would  commence  to  be  deposited  in  liquid 
form,  and  care  has  to  be  taken  to  prevent  a 
greater  lowering  of  temperature.  A  mechanical 
contrivance  known  as  the  exhauster  is  next  used," 
by  which  the  gas  is,  amongst  other'things,  helped 
forward  in  its  onwafd  movement  through  'the  ap- 
paratus. The  gas  then  passes  to  the  washers  or 


FIG.  36. 

scrubbers,  a  series  of  tall  towers,  from  which  water 
is  allowed  to  fall  as  a  fine  spray,  and  by  means  of 
which  large  quantities  of  ammonia,  sulphuretted 
hydrogen,  carbonic  acid  and  oxide,  and  cyanogen 
compounds,  are  removed.  In  the  scrubber  the 
water  used  in  keeping  the  coke,  with  which  it  is 
filled,  damp,  absorbs  these  compounds,  and  the 
union  of  the  ammonia  with  certain  of  them  takes 
place,  resulting  in  the  formation  of  carbonate  of 
ammonia  (smelling  salts),  sulphide  and  sulpho- 
cyanide  of  ammonia. 


120 


THE   STORY  OF  A   PIECE   OF   COAL. 


Hitherto  the  purification  of  the  gas  has  been 
brought  about  by  mechanical  means,  but  the  gas 
now  enters  the  "purifier"  in  which  it  undergoes 
a  further  cleansing,  but  this  time  by  chemical 
means.  The  agent  used  is  either  lime  or  hydrated 


FIG.  37. 

oxide  of  iron,  and  by  their  means  the  gas  is 
robbed  of  its  carbonic  acid  and  the  greater  part 
of  its  sulphur  compounds.  The  process  is  then 
considered  complete,  and  the  gas  passes  on  into 
the  water  chamber  over  which  the  gas-holder  is 
reared,  and  in  which  it  rises  through  the  water, 
forcing  the  huge  cylinder  upward  according  to 
the  pressure  it  exerts. 

The  gas-holder  is  poised  between  a  number  of 


HOW  GAS  IS  MADE,   ETC. 


121 


upright  pillars  by  a  series  of  chains  and  pulleys, 
which  allow  of  its  easy  ascent  or  descent  accord- 
ing as  the  supply  is  greater  or  less  than  that 
drawn  from  it  by  the  gas  mains. 

When  we  see  the  process  which  is  necessary 
in  order  to  obtain  pure  gas,  we  begin  to  appreci- 
ate to  what  an  extent  the  atmosphere  is  fouled 
when  many  of  the  products  of  distillation,  which, 
as  far  as  the  production  of  gas  is  concerned,  may 


FIG.  38. 

be  called  impurities,  are  allowed  to  escape  free 
without  let  or  hindrance.  In  these  days  of  strict 
san:tary  inspection  it  seems  strange  that  the  air 
in  che  neighbourhood  of  gas-works  is  still  al- 
lowed to  become  contaminated  by  the  escape  of 
impure  compounds  from  the  various  portions  of 
the  gas-making  apparatus.  Go  where  one  may, 
the  presence  of  these  compounds  is  at  once  ap- 
parent to  the  nostrils  wit.hin  a  none  too  limited 
area  around  them,  and  yet  their  deleterious 


122          THE   STORY  OF  A   PIECE   OF   COAL. 

effects  can  be  almost  reduced  to  a  minimum  by 
the  use  of  proper  purifying  agents,  and  by  a 
scientific  oversight  of  the  whole  apparatus.  It 
certainly  behoves  all  sanitary  authorities  to  look 
well  after  any  gas-works  situated  within  their 
districts. 

Now  let  us  see  what  these  first  five  products 
of  distillation  actually  are. 

Firstly,  illuminating-gas.  Everybody  knows 
what  this  is.  It  cannot,  however,  be  stated  to  be 
any  one  gas  in  particular,  since  it  is  a  mechanical 
mixture  of  at  least  three  different  gases,  and 
often  contains  small  quantities  of  others. 

A  very  large  proportion  consists  of  what  is 
known  as  marsh-gas,  or  light  carburetted  hydro- 
gen. This  occurs  occluded  or  locked  up  in  the 
pores  of  the  coal,  and  often  oozes  out  into  the 
galleries  of  coal-mines,  where  it  is  known  as  fine- 
damp  (German  dampf,  vapour).  It  is  disengaged 
wherever  vegetable  matter  has  fallen  and  has 
become  decayed.  If  it  were  thence  collected, 
together  with  an  admixture  of  ten  times  its 
volume  of  air,  a  miniature  coal-mine  explosion 
could  be  produced  by  the  introduction  of  a 
match  into  the  mixture.  Alone,  however,  it 
burns  with  a  feebly  luminous  flame,  although  to 
its  presence  our  house-gas  owes  a  great  portion 
of  its  heating  power.  Marsh-gas  is  the  first  of  the 
series  of  hydrocarbons  known  chemically  as  the 
paraffins,  and  is  an  extremely  light  substance, 
being  little  more  than  half  the  weight  of  an 
equal  bulk  of  air.  It  is  composed  of  four  atoms 
of  hydrogen  to  one  of  carbon  (CH4). 

Marsh-gas,  together  with  hydrogen  and  the 
monoxide  of  carbon,  the  last  of  which  burns 
with  a  dull  blue  flame  often  seen  at  the  surface 


HOW  GAS   IS   MADE,    ETC.  123 

of  fires,  particularly  coke  and  charcoal  fires, 
form  about  87  per  cent,  of  the  whole  volume  of 
coal-gas,  and  are  none  of  them  anything  but  poor 
illuminants. 

The  illuminating  power  of  coal-gas  depends 
on  the  presence  therein  of  olefiant.gas  (ethylene), 
or,  as  it  is  sometimes  termed,  heavy  carburetted 
hydrogen.  This  is  the  first  of  the  series  of 
hydro-carbons  known  as  the  defines,  and  is  com- 
posed of  two  atoms  of  carbon  to  every  four 
atoms  of  hydrogen  (C2H4).  Others  of  the  olefines 
are  present  in  minute  quantities.  Th'ese  assist 
in  increasing  the  illuminosity,  which  is  sometimes 
greatly  enhanced,  too,  by  t'he  presence  of  a  small 
quantity  of  benzene  vapour.  These  illuminants, 
however,  constitute  but  about  6  per  cent,  of  the 
whole. 

Added  to  these,  there  are  four  other  usual 
constituents  which  in  no  way  increase  the  value 
of  gas,  but  which  rather  detract  from  it.  They 
are  consequently  as  far  as  possible  removed  as 
impurities  in  the  process  of  gas-making.  These 
are  nitrogen,  carbonic  acid  gav^nd  the  destruc- 
tive sulphur  compounds,  sulphuretted  hydrogen 
and  carbon  bisulphide  vapour.  It  is  to  the  last 
two  to  which  are  to  be  attributed  the  injurious 
effects  which  the  burning,  of  gas  has  upon  pictures, 
books,  and  also  the  tarnishing  which  metal  fittings 
suffer  where  gas  is  burnt,  since  they  give  rise  to 
the  formation  of  oil  of  vitriol  (sulphuric  acid), 
which  is  being  incessantly  poured  into  the  air. 
Of  course  the  amount  so  given  off  is  little  as 
compared  with  that  which  escapes  from  a  coal 
fire,  but,  fortunately  for  the  inmates  of  the  room, 
in  this  case  the  greater  quantity  goes  up  the 
chimney ;  this,  however,  is  but  a  method  of  post- 


124  THE  STORY  OF  A  PIECE  OF  COAL. 

poning  the  evil  day,  until  the  atmosphere  becomes 
so  laden  with  impurities  that  what  proceeds  at 
first  up  the  chimney  will  finally  again  make  its 
way  back  through  the  doors  and  windows.  A 
recent  official  report  tells  us  that,  in  the  town 
of  St.  Helen's  alone,  sufficient  sulphur  escapes 
annually  into  the  atmosphere  to  finally  produce 
110,580  tons  of  sulphuric  acid,  and  a  computation 
has  been  made  that  every  square  mile  of  land  in 
London  is  deluged  annually  with  180  tons  of  the 
same  vegetation-denuding  acid.  It  is  a  matter 
for  wonder  that  any  green  thing  continues  to  ex- 
ist in  such  places  at  all. 

The  chief  constituents  of  coal-gas  are,  there- 
fore, briefly  as  follows : — 

(1)  Hydrogen, 

(2)  Marsh-gas  (carburetted  hydrogen  or  fire- 

damp), 

(3)  Carbon  monoxide, 

(4)  Olefiant    gas    (ethylene,    or  heavy   carbu- 

retted hydrogen),  with  other  olefines, 

(5)  Nitrogen, 

(6)  Carbonic  acid  gas, 

(7)  Sulphuretted  hydrogen, 

(8)  Carbon  bisulphide  (vapour), 

the  last  four  being  regarded  as  impurities,  which 
are  removed  as  far  as  possible  in  the  manufac- 
ture. 

In  the  process  of  distillation  of  the  coal,  we 
have  seen  that  various  other  important  sub- 
stances are  brought  into  existence.  The  final 
residue  of  coke,  which  is  impregnated  with  the 
sulphur  which  has  not  been  volatilised  in  the  form 
of  sulphurous  gases,  we  need  scarcely  more  than 


HOW  GAS   IS  MADE,   ETC.  125 

mention  here.  But  the  gas-tar  and  the  ammo- 
niacal  liquor  are  two  important  products  which 
demand  something  more  than  our  casual  atten- 
tion. At  one  time  regarded  by  gas  engineers  as 
unfortunately  necessary  nuisances  in  the  manu- 
facture of  gas,  they  have  both  become  so  valuable 
on  account  of  materials  which  can  be  obtained 
from  them,  that  they  enable  gas  itself  to  be  sold 
now  at  less  than  half  its  original  price.  The 
waste  of  former  generations  is  being  utilised  in 
this,  and  an  instance  is  recorded  in  which  tar, 
which  was  known  to  have  been  lying  useless  at  the 
bottom  of  a  canal  for  years,  has  been  purchased  by 
a  gas  engineer  for  distilling  purposes.  It  has 
been  estimated  that  about  590,000  tons  of  coal- 
tar  are  distilled  annually. 

Tar  in  its  primitive  condition  has  been  used, 
as  every  one  is  aware,  for  painting  or  tarring  a 
variety  of  objects,  such  as  barges  and  palings,  in 
fact,  as  a  kind  of  protection  to  the  object  covered 
from  the  ravages  of  insects  and  worms,  or  to  pre- 
vent corrosion  when  applied  to  metal  piers.  But 
it  is  worthy  of  a  better  purpose,  and  is  capable 
of  yielding  far  more  useful  and  interesting  sub- 
stances than  even  the  most  imaginative  individual 
could  have  dreamed  of  fifty  years  ago. 

In  the  process  of  distillation,  the  tar,  after 
standing  in  tanks  for  some  time,  in  order  that 
any  ammoniacal  liquor  which  may  be  present 
may  rise  to  the  surface  and  be  drawn  off,  is 
pumped  into  large  stills,  where  a  moderate  amount 
of  heat  is  applied  to  it.  The  result  is  that  some 
of  the  more  volatile  products  pass  over  and  are 
collected  in  a  receiver.  These  first  products  are 
known  as  first  light  oils,  or  crude  coal-naphtha,  and 
to  this  naphtha  all  the  numerous  natural  naphthas 


126  THE  STORY  OF  A   PIECE  OF  COAL. 

which  have  been  discovered  in  various  portions 
of  the  world,  and  to  wrhich  have  been  applied 
numerous  local  names,  bear  a  very  close  resem- 
blance. Such  an  one,  for  instance,  was  that  small 
but  famous  spring  at  Riddings,  in  Derbyshire, 
from  which  the  late  Mr.  Young — Paraffin  Young 
— obtained  his  well-known  paraffin  oil,  which  gave 
the  initial  impetus  to  what  has  since  developed 
into  a  trade  of  immense  proportions  in  every 
quarter  of  the  globe. 

After  a  time  the  crude  coal-naphtha  ceases  to 
flow  over,  and  the  heat  is  increased.  The  result 
is  that  a  fresh  series  of  products,  known  as  medium 
oils,  passes  over,  and  these  oils  are  again  collected 
and  kept  separate  from  the  previous  series. 
These  in  turn  cease  to  flow,  when,  by  a  further 
increase  of  heat,  what  are  known  as  the  heavy 
oils  finally  pass  over,  and  when  the  last  of  these, 
the  "green  grease,"  distils  over,  pitch  alone  is  left 
in  the  still.  Pitch  is  used  to  a  large  extent  in  the 
preparation  of  artificial  asphalt,  and.  also  of  a  fuel 
known  as  "briquettes." 

The  products  thus  obtained  at  the  various 
stages  of  the  process  are  themselves  subjected 
to  further  distillation,  and  by  the  exercise  of 
great  care,  requiring  the  most  delicate  and  accu- 
rate treatment,  a  large  variety  of  oils  is  obtained, 
and  these  are  retailed  under  many  and  various 
fanciful  names. 

/  One  of  the  most  important  and  best  known 
products  of  the  fractional  distillation  of  crude 
coal-naphtha  is  that  known  as  benzene,  or  benzole, 
(C6H6).  This,  in  its  unrefined  condition,  is  a  light 
spirit  which  distils  over  at  a  point  somewhat  be- 
low the  boiling  point  of  water,  but  a  delicate  pro- 
cess of  rectification  is  necessary  to  produce  the 


HOW  GAS   IS  MADE,   ETC.  127 

pure  spirit.  Other  products  of  the  same  light 
oils  are  toluene  and  xylene. 

Benzene  of  a  certain  quality  is  a  very  familiar 
and  useful  household  article.  In  America  light 
oils  from  petroleum  are  sold  under  this  name.  It 
is  used  for  removing  grease  from  clothing,  clean- 
ing kid  gloves,  &c.  If  pure  it  is  in  reality  a  most 
dangerous  spirit,  being  very  inflammable;  it  is 
also  extremely  volatile,  so  much  so  that,  if  an  un- 
corked bottle  be  left  in  a  warm  room  where  there 
is  a  fire  or  other  light  near,  its  vapour  will  prob- 
ably ignite.  Should  the  vapour  become  mixed 
with  air  before  ignition,  it  becomes  a  most  dan- 
gerous explosive,  and  it  will  thus  be  seen  how 
necessary  it  is  to  handle  the  article  in  household 
use  in  a  most  cautious  manner.  Being  highly 
volatile,  a  considerable  degree  of  cold  is  experi- 
enced if  a  drop  be  placed  on  the  hand  and  allowed 
to  evaporate. 

Benzene,  which  is  only  a  compound  of  carbon 
and  hydrogen,  was  first  discovered  by  Faraday  in 
1825  ;  it  is  now  obtained  in  large  quantities  from 
coal-tar,  not  so  much  for  use  as  benzene  as  for 
its  conversion,  in  the  first  place,  by  the  action  of 
nitric  acid,  into  nitro  benzole,  a  liquid  having  an 
odour  like  the  oil  of  bitter  almonds,  and  which  is 
much  used  by  perfumers  under  the  name  of  essence 
de  mirbane;  and,  in  the  second  place,  for  the  pro- 
duction from  this  nitro-benzole  of  the  far-famed 
aniline.  After  the  distillation  of  benzene  from  the 
crude  coal-naphtha  is  completed,  the  chief  im- 
purities in  the  residue  are  charred  and  deposited 
by  the  action  of  strong  sulphuric  acid.  By  further 
Distillation  a  lighter  oil  is  given  off,  often  known 
\as  artificial  turpentine  oil,  which  is  used  as  a  solvent 
for  varnishes  and  lackers.  This  is  very  familiar 


128  THE  STORY  OF  A  PIECE  OF  COAL. 

to  the  costermonger  of  London  as  the  oil  which 
is  burned  in  the  flaring  lamps  which  illuminate 
the  New  Cut  or  the  Elephant  and  Castle  on  Satur- 
day and  other  market  nights. 

By  distillation  of  the  heavy  oils,  carbolic  acid 
and  commercial  anthracene  are  produced,  and  by  a 
treatment  of  the  residue,  a  white  and  crystalline 
substance  known  as  naphthalin  (C10H8)  is  finally 
obtained. 

Thus,  by  the  continued  operation  of  the  chem- 
ical process  known  as  fractional  distillation  of  the 
immediate  products  of  coal-tar,  these  various 
series  of  useful  oils  are  prepared. 

The  treatment  is  much  the  same  which  has  re- 
sulted in  the  production  of  paraffin  oil,  to  which 
we  have  previously  referred,  and  an  account  of 
the  production  of  coal-oils  would  be  very  far  from 
satisfactory,  which  made,  no  mention  of  the  pro- 
duction of  similar  commodities  by  the  direct  dis- 
tillation of  shale.  Oil-shales,  or  bituminous  shales, 
exist  in  all  parts  of  the  world,  and  may  be  re- 
garded as  mineral  matter  largely  impregnated  by 
the  products  of  decaying  vegetation.  They  there- 
fore greatly  resemble  some  coals,  and  really  only 
differ  therefrom  in  degree,  in  the  quantity  of  vege- 
table matter  which  they  contain.  Into  the  sub- 
ject of  the  various  native  petroleums  which  have 
been  found — for  these  rock-oils  are  better  known 
as  petroleums — in  South  America,  in  Burmah 
(Rangoon  Oil),  at  Baku,  and  the  shores  of  the 
Caspian,  or  in  the  United  States  of  America,  we 
need  not  enter,  except  to  note  that  in  all  proba- 
bility the  action  of  heat  on  underground  bitumi- 
nous strata  of  enormous  extent  has  been  the  cause 
of  their  production,  just  as  on  a  smaller  scale  the 
action  of  artificial  heat  has  forced  the  reluctant 


HOW  GAS   IS  MADE,   ETC.  129 


shale  to  give  up  its  own  burden  of  mineral  oil. 
However,  previous  to  1847,  although  native  min- 
eral oil  had  been  for  some  years  a  recognised 
article  of  commerce,  the  causes  which  give  rise  to 
the  oil-wells,  ?nd  the  source,  probably  a  deep- 
seated  one,  oi  the  supply  of  oil,  does  not  appear 
to  have  been  well  known,  or  at  least  was  not  en- 
quired after.  But  in  that  year  Mr.  Young,  a 
chemist  at  Manchester,  discovered  that  by  distil- 
ling some  petroleum,  which  he  obtained  from  a 
spring  at  Riddings  in  Derbyshire,  he  was  able  to 
procure  a  light  oil,  which  he  used  for  burning  in 
lamps,  whilst  the  heavier  product  which  he  also 
obtained  proved  a  most  useful  lubricant  for  ma- 
chinery. This  naturally  distilled  oil  was  soon 
found  to  be  similar  to  that  oil  which  was  noticed 
dripping  from  the  roof  of  a  coal-mine.  Judging 
that  the  coal,  being  under  the  influence  of  heat, 
was  the  cause  of  the  production  of  the  oil,  Mr. 
Young  tested  this  conclusion  by  distilling  the 
coal  itself.  Success  attended  his  endeavour  thus 
to  procure  the  oil,  and  indelibly  Young  stamped 
his  name  upon  the  roll  of  famous  men,  whose  in- 
dustrial inventions  have  done  so  much  towards 
the  accomplishment  of  the  marvellous  progress 
of  the  present  century.  From  the  distillation  he 
obtained  the  well-known  Young's  Paraffin  Oil, 
and  the  astonishing  developments  of  the  process 
which  have  taken  place  since  he  obtained  his 
patent  in  1850,  for  the  manufacture  of  oils  and 
solid  paraffin,  must  have  been  a  source  of  great 
satisfaction  to  him  before  his  death,  which  oc- 
curred in  1883. 

Cannel  coal,  Boghead  or  Bathgate  coal,  and 
bituminous  shales  of  various  qualities,  have  all 
been  requisitioned  for  the  production  of  oils,  and 
9 


130  THE  STORY  OF  A   PIECE  OF  COAL. 

from  these  various  sources  the  crude  naphthas, 
which  bear  a  variety  of  names  according  to  some 
peculiarity  in  their  origin,  or  place  of  occur- 
rence, are  obtained.  Boghead  coal,  also  known 
as  "Torebanehill  mineral,"  gives  Boghead  naph- 
tha, while  the  crude  naphtha  obtained  from  shales 
is  often  quoted  as  shale-oil.  In  chemical  com- 
position these  naphthas  are  closely  related  to  one 
another,  and  by  fractional  distillation  of  them 
similar  series  of  products  are  obtained  as  those 
we  have  already  seen  as  obtained  from  the  crude 
coal-naphtha  of  coal-tar. 

In  the  direct  distillation  of  cannel  coal  for 
the  production  of  paraffin,  it  is  necessary  that  the 
perpendicular  tubes  or  retorts  into  which  the  coal 
is  placed  be  heated  only  to  a  certain  tempera- 
ture, which  is  considerably  lower  than  that  ap- 
plied when  the  object  is  the  production  of  coal- 
gas.  By  this  means  nearly  all  the  volatile  matters 
pass  over  in  the  form  of  condensible  vapours,  and 
the  crude  oils  are  at  once  formed,  from  which 
are  obtained  at  different  temperatures  various 
volatile  ethers,  benzene,  and  artificial  turpentine 
oil  or  petroleum  spirit.  After  these,  safety-burn- 
ing paraffin  oil,  or  kerosene,  follows,  but  it  is 
essential  that  the  previous  three  volatile  products 
be  completely  cleared  first,  since,  mixed  with  air, 
they  form  highly  dangerous  explosives.  To  the 
fact  that  the  operation  is  carried  on  in  the  manu- 
factories with  great  care  and  accuracy  can  only 
be  attributed  the  comparative  rareness  of  explo- 
sions of  the  oil  used  in  households. 

After  parafiS^v^e^heavy  lubricating  oils  are 
next  given  off,  still  increasing  the  temperature, 
and,  the  residue  being  in  turn  subjected  to  a  very 
low  temperature,  the  white  solid  substance  known 


HOW  GAS   IS  MADE,    ETC.  131 

as  paraffin,  so  much  used  for  making  candles,  is 
the  result.     By  a  different  treatment  of  the  same 

I  residue  is  produced  that  wonderful  salve  for  ten- 
der skins,  cuts,  and  burns,  known  popularly  as 

\vaseline.      Probably    no    such    widely-advertised 

^remedial  substance  has  so  deserved  its  success  as 

this  universally  used  waste  product  of  petroleum. 

We  have  noticed  the  fact  that  in  order  to  pro- 

\  cure  safety-burning  oils,  it  is  absolutely  neces- 

£  sary  that  the  more  volatile  portions  be  completely 
distilled  over  first.  In  most  countries  where  these 

I  oils  are  much  used  a  test  is  applied  to  them  which 
consists  in  determining  the  flashing-point.  Many 
of  the  more  volatile  ethers,  which  are  highly  in- 
flammable, are  given  off  even  at  ordinary  tem- 

.  peratures,  and  the  application  of  a  light  to  the 
oil  will  cause  the  volatile  portion  to  "  flash,"  as  it 
is  called.  A  safe  kerosene,  according  to  the  laws 
of  many  of  the  United  States,  must  not  flash 
under  100°  Fahrenheit  open  test,  and  all  those 
portions  which  flash  at  a  less  temperature  must  be 
volatilised  off  before  the  residue  can  be  deemed  a 
safe  oil.  It  seems  probable  that  the  flashing- 

:  point  will  sooner  or  later  be  raised. 

One  instance  may  be  cited  to  show  how  neces- 
sary it  is  that  the  native  mineral  oils  which  have 
been  discovered  should  have  this  effectual  test 
applied  to  them. 

When  the  oil-wells  were  first  discovered  in 
America,  the  oil  was  obtained  simply  by  a  pro- 
cess of  boring,  and  the  fountain  of  oil  which  was 
bored  into  at  times  was  so  prolific,  that  it  rushed 
out  with  a  force  which  carried  all  obstacles  before 
it,  and  defied  all  control.  In  one  instance  a  col- 
umn of  oil  shot  into  the  air  to  a  height  of  forty 
feet,  and  defied  all  attempts  to  keep  it  under.  In 


132  THE  STORY  OF  A   PIECE  OF  COAL. 

order  to  prevent  further  accident,  all  lights  in 
the  immediate  neighbourhood  were  extinguished, 
the  nearest  remaining  being  at  a  distance  of  four 
hundred  feet.  But  in  this  crude  naphtha  there 
was,  as  usual,  a  quantity  of  volatile  spirit  which 
was  being  given  off  even  at  the  temperature  of 
the  surrounding  atmosphere.  This  soon  became 
ignited,  and  with  an  explosion  the  column  of  oil 
was  suddenly  converted  into  a  roaring  column  of 
fire.  The  owner  of  the  property  was  thrown  a 
distance  of  twenty  feet  by  the  explosion,  and 
soon  afterwards  died  from  the  burns  which-  he 
had  received  from  it.  Such  an  accident  could 
not  now,  however,  happen.  The  tapping,  stop- 
ping, and  regulating  of  gushing  wells  can  now  be 
more  effectually  dealt  with,  and  in  the  process  of 
refining,  the  most  inflammable  portions  are  sepa- 
rated, with  a  result  that,  as  the  use  of  oil  which 
flashes  under  100°  F.  open  test  is  generally  for- 
bidden, and  as  our  normal  temperature  is  con- 
siderably less  than  this,  there  is  little  to  be  feared 
in  the  way  of  explosion  if  the  law  be  complied 
with. 

When  the  results  of  Mr.  Young's  labours  be- 
came publicly  known,  a  number  of  companies 
were  started  with  the  object  of  working  on  the 
lines  laid  down  in  his  patent,  and  these  not  only 
in  Great  Britain  but  also  in  the  United  States, 
whither  quantities  of  cannel  coal  were  shipped 
from  England  and  other  parts  to  feed  the  retorts. 
In  1860,  according  to  the  statistics  furnished, 
some  seventy  factories  were  established  in  the 
United  States  alone  with  the  object  of  extracting 
oil  from  coal  and  other  mineral  sources,  such  as 
bituminous  shale,  etc.  When  Young's  patent 
finally  expired,  a  still  greater  impetus  was  given 


HOW  GAS  IS  MADE,   ETC.  133 

to  its  production,  and  the  manufacture  would 
probably  have  continued  to  develop  were  it  not 
that  attention  had,  two  years  previously,  been 
forcibly  turned  to  those  discoveries  of  great 
stores  of  natural  oil  in  existence  beneath  a  com- 
paratively thin  crust  of  earth,  and  which,  when 
bored  into,  spouted  out  to  tremendous  heights. 

The  discovery  of  these  oil-fountains  entirely 
supplanted  the  industry  in  America  and  checked 
its  development  in  England,  but  with  the  great  pro- 
duction there  has  apparently  been  a  greatly  in- 
creased demand  for  it,  and  the  British  industry 
once  again  appears  to  thrive,  until  even  bitumi- 
nous shales  have  been  brought  under  requisition 
for  their  contribution  to  the  national  wealth. 

Were  it  not  for  the  nuisance  and  difficulty 
experienced  in  the  proper  cleaning  and  trimming 
of  lamps,  there  seems  no  other  reason  why  min- 
eral oil  should  not  in  turn  have  superseded  the 
use  of  gas,  even  as  gas  had,  years  before,  super- 
seded the  expensive  animal  and  vegetable  oils 
which  had  formerly  been  in  use.* 

Although  this  great  development  in  the  use  of 
mineral  oils  has  taken  place  only  within  the  last 
thirty  years,  it  must  not  be  thought  that  their 
use  is  altogether  of  modern  invention.  That 
they  were  not  altogether  unknown  in  the  fifth 
century  before  Christ  is  a  matter  of  certainty, 
and  at  the  time  when  the  Persian  Empire  was  at 
the  zenith  of  its  glory,  the  fires  in  the  temples  of 
the  fire-worshippers  were  undoubtedly  kept  fed 
by  the  natural  petroleum  which  the  districts 
around  afforded.  It  is  thought  by  some  that  the 
legend  which  speaks  of  the  fire  which  came  down 
from  heaven,  and  which  lit  the  altars  of  the 
Zoroastrians,  may  have  had  its  origin  in  the 


134  THE  STORY  OF  A  PIECE  OF  COAL. 

discovery  of  a  hitherto  unknown  petroleum 
spring.  More  recently,  the  remarks  of  Marco 
Polo  in  his  account  of  his  travels  in  A.  D.  1260 
and  following  years,  are  particularly  interesting 
as  showing  that,  even  then,  the  use  of  mineral 
oil  for  various  purposes  was  not  altogether  un- 
known. He  says  that  on  the  north  of  Armenia 
the  Greater  is  "  Zorzania,  in  the  confines  of 
which  a  fountain  is  found,  from  which  a  liquor 
like  oil  flows,  and  though  unprofitable  for  the 
seasoning  of  meat,  yet  is  very  fit  for  the  supply- 
ing of  lamps,  and  to  anoint  other  things;  and 
this  natural  oil  flows  constantly,  and  that  in 
plenty  enough  to  lade  camels." 

From  this  we  can  infer  that  the  nature  of  the 
oil  was  entirely  unknown,  for  it  was  a  "  liquor 
like  oil,"  and  was  also,  strange  to  say,  "  unprofit- 
able for  the  seasoning  of  meat  "  !  In  another 
place  in  Armenia,  Marco  Polo  states  that  there 
was  a  fountain  "  whence  rises  oil  in  such  abun- 
dance that  a  hundred  ships  might  be  at  once 
loaded  with  it.  It  is  not  good  for  eating,  but 
very  fit  for  fuel,  for  anointing  the  camels  in 
maladies  of  the  skin,  and  for  other  purposes; 
for  which  reason  people  come  from  a  great  dis- 
tance for  it,  and  nothing  else  is  burned  in  all  this 
country." 

The  remedial  effects  of  the  oil,  when  used  as 
an  ointment,  were  thus  early  recognised,  and  the 
far-famed  vaseline  of  the  present  day  may  be  re- 
garded as  the  lineal  descendant,  so  to  speak,  of 
the  crude  medicinal  agent  to  which  Marco  Polo 
refers. 

The  term  asphalt  has  been  applied  to  so  many 
and  various  mixtures,  that  one  scarcely  associates 
it  with  natural  mineral  pitch  which  is  found  in 


HOW  GAS  IS  MADE,   ETC.  135 

some  parts  of  the  world.  From  time  immemorial 
this  compact,  bituminous,  resinous  mineral  has 
been  discovered  in  masses  on  the  shores  of  the 
Dead  Sea,  which  has  in  consequence  received  the 
well-known  title  of  Lake  Asphaltites.  Like  the 
naphthas  and  petroleums  which  have  been  noticed, 
this  has  had  its  origin  in  the  decomposition  of 
vegetable  matter,  and  appears  to  be  thrown  up 
in  a  liquid  form  by  the  volcanic  energ'es  which 
are  still  believed  to  be  active  in  the  centre  of 
the  lake,  and  which  may  be  existent  beneath  a 
stratum,  or  bed,  of  oil-producing  bitumen. 

In  connection  with  the  formation  of  this 
substance,  the  remarks  of  Sir  Charles  Lyell, 
the  great  geologist,  may  well  be  quoted  as  show- 
ing the  transformation  of  vegetable  matter  into 
petroleum,  and  afterwards  into  solid-looking 
asphalt.  At  Trinidad  is  a  lake  of  bitumen 
which  is  a  mile  and  a  half  in  circumference. 
"The  Orinoco  has  for  ages  been  rolling  down 
great  quantities  of  woody  and  vegetable  bodies 
into  the  surrounding  sea,  where,  by  the  influence 
of  currents  and  eddies,  they  may  be  arrested,  and 
accumulated  in  particular  places.  The  frequent 
occurrence  of  earthquakes  and  other  indications 
of  volcanic  action  in  those  parts,  lend  counte- 
nance to  the  opinion  that  these  vegetable  sub- 
stances may  have  undergone,  by  the  agency 
of  subterranean  fire,  those  transformations  or 
chemical  changes  which  produce  petroleum;  and 
this  may,  by  the  same  causes,  be  forced  up  to  the 
surface,  where,  by  exposure  to  the  air,  it  becomes 
inspissated,  and  forms  those  different  varieties 
of  earth-pitch  or  asphaltum  so  abundant  in  the 
island." 

It  is  interesting  to  note  also  that  it  was  ob- 


136  THE  STORY  OF  A   PIECE  OF   COAL. 

tained,  at  an  ancient  period,  from  the  oil-fountains 
of  Is,  and  that  it  was  put  to  considerable  use  in 
the  embalming  of  the  bodies  of  the  Egyptians.  It 
appears,  too,  to  have  been  employed  in  the  con- 
struction of  the  walls  of  Babylon,  and  thus  from 
very  early  times  these  wonderful  products  and 
results  of  decayed  vegetation  have  been  brought 
into  use  for  the  service  of  man. 

Aniline  has  been  previously  referred  to  (p.  127) 
as  having  been  prepared  from  nitro-benzole,  or 
essence  de  mirbane,  and  its  preparation,  by  treating 
this  substance  with  iron-filings  and  acetic  acid, 
was  one  of  the  early  triumphs  of  the  chemists 
who  undertook  the  search  after  the  unknown 
contained  in  gas-tar.  It  had  previously  been  ob- 
tained from  oils  distilled  from  bones.  The 
importance  of  the  substance  lies  in  the  fact 
that,  by  the  action  of  various  chemical  reagents, 
a  series  of  colouring  matters  of  very  great  rich- 
ness are  formed,  and  these  are  the  well-known 
aniline  dyes. 

As  early  as  1836,  it  was  discovered  that  ani- 
line, when  heated  with  chloride  of  lime,  acquired 
a  beautiful  blue  tint.  This  discovery  led  to  no 
immediate  practical  result,  and  it  was  not  until 
twenty-one  years  after  that  a  further  discovery 
was  made,  which  may  indeed  be  said  to  have 
achieved  a  world-wide  reputation.  It  was  found 
that,  by  adding  bichromate  of  potash  to  a  solution 
of  aniline  and  sulphuric  acid,  a  powder  was  ob- 
tained from  which  the  dye  was  afterwards  ex- 
tracted, which  is  known  as  mauve.  Since  that 
time  dyes  in  all  shades  and  colours  have  been 
obtained  from  the  same  source.  Magenta  was 
the  next  dye  to  make  its  appearance,  and  in  the 
fickle  history  of  fashion,  probably  no  colours 


HOW  GAS  IS   MADE,   ETC.  137 

had  such  extraordinary  runs  of  popularity  as 
those  of  mauve  and  magenta.  Every  conceivable 
colour  was  obtained  in  due  course  from  the  same 
source,  and  chemists  began  to  suspect  that,  in  the 
course  of  time,  the  colouring  matter  of  dyer's 
madder,  which  was  known  as  alizarin,  would 
also  be  obtained  therefrom.  Hitherto  this  had 
been  obtained  from  the  root  of  the  madder-plant, 
but  by  dint  of  careful  and  well-reasoned  research, 
it  was  obtained  by  Dr.  Groebe,  from  a  solid 
crystalline  coal-tar  product,  known  as  anthracene, 
(C12H14).  This  artificial  alizarin  yields  colours 
which  are  purer  than  those  of  natural  madder, 
and  being  derived  from  what  was  originally  re- 
garded as  a  waste  product,  its  cost  of  production 
is  considerably  cheaper. 

We  have  endeavoured  thus  far  to  deal  with 

/  (i)  gas,  and  (2)  tar,  the  two  principal  products 
in  the  distillation  of  coal.  We  have  yet  to  say 

1  a  few  words  concerning  the  useful  ammoniacai 
liquor,  and  the  final  residue  in  the  retorts,  /.  e., 
coke. 

The  ammoniacai  liquor  which  has  been  pass- 
ing over  during  distillation  of  the  coal,  and  which 
has  been  collecting  in  the  hydraulic  main  and  in 
other  parts  of  the  gas-making  apparatus,  is  set 
aside  to  be  treated  to  a  variety  of  chemical  re- 
actions, in  order  to  wrench  from  it  its  useful  cour 
stituents.  Amongst  these,  of  course,  ammonia] 
stands  in  the  first  rank,  the  others  being  compar- 
atively unimportant.  '  In  order  to  obtain  this,  the 
liquor  is  first  of  all  neutralised  by  being  treated 
with  a  quantity  of  acid,  which  converts  the  prin- 
cipal constituent  of  the  liquor,  viz.,  carbonate 
of  ammonia  (smelling  salts),  into  either  sulphate 
of  ammonia,  or  chloride  of  ammonia,  familiarly 


138  THE   STORY  OF  A   PIECE  OF  COAL. 

known  as  sal-ammoniac,  acco'rding  as  sulphuric 
acid  or  hydrochloric  acid  is  the  acid  used.  Thus 
carbonate  of  ammonia  with  sulphuric  acid  will  give 
sulphate  of  ammonia,  but  carbonate  of  ammonia 
with  hydrochloric  acid  will  give  sal-ammoniac 
(chloride  of  ammonia).  By  a  further  treatment 
of  these  with  lime,  or,  as  it  is  chemically  known, 
oxide  of  calcium,  ammonia  is  set  free,  whilst 
chloride  of  lime  (the  well-known  disinfectant),  or 
sulphate  of  lime  (gypsum,  or  "  plaster  of  Paris  "), 
is  the  result. 
Thus: 

Sulphate  of  ammonia  +  lime  =  plaster  of  Paris  +  ammonia, 
or, 
Sal-ammoniac  +  lime  =  chloride  of  lime  +  ammonia. 

Ammonia  itself  is  a  most  powerful  gas,  and 
acts  rapidly  upon  the  eyes.  It  has  a  stimulating 
effect  upon  the  nerves.  It  is  not  a  chemical  ele- 
ment, being  composed  of  three  parts  of  hydrogen 
by  weight  to  one  of  nitrogen,  both  of  which  ele- 
ments alone  are  very  harmless,  and  the  latter, 
indeed,  very  necessary  to  human  .life.  Ammonia 
is  fatal  to  life,  producing  great  irritation  of  the 
lungs. 

It  has  also  been  called  "  hartshorn,"  being 
obtained  by  destructive  distillation  of  horn  and 
bone.  The  name  "  ammonia "  is  said  to  have 
been  derived  from  the  fact  that  it  was  first  ob- 
tained by  the  Arabs  near  the  temple  of  Jupiter 
Ammon,  in  Lybia,  North  Africa,  from  the  ex- 
crement of  camels,  in  the  form  of  sal-ammoniac. 
There  are  always  traces  of  it  in  the  atmosphere, 
especially  in  the  vicinity  of  large  towns  and 
manufactories  where  large  quantities  of  coal  are 
burned. 


HOW  GAS  IS   MADE,   ETC.  139 

Coke,  if  properly  prepared,  should  consist  of 
pure  carbon.  Good  coal  should  yield  as  much  as 
80  per  cent,  of  coke,  but  owing  to  the  unsatisfac- 
tory manner  of  its  production,  this  proportion  is 
seldom  yielded.  The  coke  which  is  left  in  the 
retorts  after  gas-making  is  sold  to  bakeries, 
laundries,  factories,  and  also  for  household  pur- 
poses. It  kindles  easily  and  burns  rapidly,  hence 
it  is  especially  useful  when  a  quick  hot  fire  is 
wanted,  and  it  is  also  employed  to  aid  the  burn- 
ing of  hard  coal.  Naturally  a  coke  fire  must  be 
replenished  oftener  than  one  of  coal.  In  the 
household  it  is  said  that  owing  to  the  quantity  of 
oxygen  required  in  its  combustion,  it  gives  rise  to 
feelings  of  suffocation  where  insufficient  ventila- 
tion of  the  room  is  provided. 

Large  quantities  of 'coke  are,  however,  con- 
sumed in  the  feeding  of  furnace  fires,  and  in  the 
heating  of  boilers  of  locomotives,  as  well  as  in 
metallurgical  operations;  and  in  order  to  supply 
the  demand,  large  quantities  of  coal  are  "  coked," 
a  process  by  which  the  volatile  products  are  com- 
pletely burnt  off,  pure  coke  remaining  behind. 
This  process  is  therefore  the  direct  opposite  to 
that  of  "  distillation,"  by  which  the  volatile  prod- 
ducts  are  carefully  collected  and  re-distilled. 

The  sulphurous  impurities  which  occur  in 
most  bituminous  coals,  and  which  are,  to  a  certain 
extent,  retained  in  coke  made  at  the  gas-works, 
themselves  have  a  value,  which  in  these  utilitarian 
days  is  not  long  likely  to  escape  the  attention  of 
capitalists.  In  coal,  bands  of  bright  shining  iron 
pyrites  are  frequently  seen,  even  in  the  homely 
scuttle,  and  when  coal  is  washed,  as  it  is  in  some 
places,  the  removal  of  the  pyrites  increases  the 
value  of  the  coal,  whilst  it  has  a  value  of  its  own. 


140         THE   STORY  OF  A   PIECE  OF  COAL. 

The  conversion  of  the  sulphur  contained  in 
pyritic  coal  first  into  the  very  offensive  gas,  sul- 
phuretted hydrogen,  and  then  into  sulphuric  acid, 
has  been  referred  to,  and  it  is  to  be  hoped  that  in 
these  days  when  every  available  source  of  wealth 
is  being  looked  up,  and  when  there  threatens  to 
remain  nothing  which  shall  in  the  future  be  known 
as  "  waste,"  that  the  atmosphere  will  be  spared 
being  longer  the  receptacle  for  the  unowned  and 
execrated  brimstone  of  millions  of  fires  and  fur- 
naces. 


CHAPTER   VII. 

THE    COAL    SUPPLIES    OF    THE    WORLD. 

As  compared  with  some  of  the  American  coal- 
fields, those  of  Britain  are  but  small,  both  in  ex- 
tent and  thickness.  They  can  be  regarded  as 
falling  naturally  into  three  principal  areas. 

The  northern  coal-field,  including  those  of 
Fife,  Stirling,  and  Ayr  in  Scotland  ;  Cumber- 
land, Newcastle,  and  Durham  in  England; 
Tyrone  in  Ireland. 

The  middle  coal-field,  all  geologically  in 
union,  including  those  of  Yorkskire,  Derby- 
shire, Shropshire,  Staffordshire,  Flint,  and 
Denbigh. 

The  southern  coal-field,  including  South  Wales, 
Forest  of  Dean,  Bristol,  Dover,  with  an  off- 
shoot at  Leinster,  &c.,  and  Millstreet,  Cork. 

Thus  it  will  be  seen  that  while  England  and 
Scotland  are,  in  comparison  with  their  extent  of 


THE  COAL  SUPPLIES  OF  THE  WORLD.       141 

surface,  bountifully  supplied  with  coal-areas,  in 
the  sister  island  of  Ireland  coal-producing  areas 
are  almost  absent.  The  isolated  beds  in  Cork 
and  Tipperary,  in  Tyrone  and  Antrim,  are  but 
the  remnants  left  of  what  were  formerly  beds  of 
coal  extending  the  whole  breadth  and  length  of 
Ireland.  Such  beds  as  there  remain  undoubtedly 
belong  to  the  base  of  the  coal-measures,  and 
observations  all  go  to  show  that  the  surface 
suffered  such  extreme  denudation  subsequent  to 
the  growth  of  the  coal-forests,  that  the  wealth 
which  once  lay  there,  has  been  swept  away  from 
the  surface  which  formerly  boasted  of  it. 

On  the  continent  of  Europe  the  coal-fields, 
though  not  occupying  so  large  a  proportion  of 
the  surface  of  the  country  as  in  England,  are 
very  far  from  being  slight  or  to  be  disregarded. 
The  extent  of  forest-lands  still  remaining  in^Gejr-. 
many  and  Austria  are  sufficing  for  the  immediate 
needs  of  the  districts  where  some  of  the  best 
seams  occur.  It  is  only  where  there  is  a  dearth 
of  handy  fuel,  ready  to  be  had,  perhaps,  by  the 
simple  felling  of  a  few  trees,  that  man  commences 
to  dig  into  the  earth  for  his  fuel.  But  although 
on  the  continent  not  yet  occupying  so  prominent 
a  position  in  public  estimation  as  do  coal-fields 
in  Great  Britain,  those  of  the  former  have  one 
conspicuous  characteristic,  viz.,  the  great  thick- 
ness of  some  of  the  individual  seams. 

In  the  coal-field  of  Midlothian  the  seams  of 
coal  vary  from  2  feet  to  5  feet  in  thickness. 
One  of  them  is  known  as  the  "  great  seam,"  and 
in  spite  of  its  name  attains  a  thickness  only  of 
from  8  to  10  feet  thick.  There  are  altogether 
about  thirty  seams  of  coal.  When,  however,  we 
pass  to  the  continent,  we  find  many  instances, 


142  THE   STORY  OF  A   PIECE   OF   COAL. 

such  as  that  of  the  coal-field  of  Central  France, 
in  which  the  seams  attain  vast  thicknesses,  many 
of  them  actually  reaching  40  and  60  feet,  and 
sometimes  even^So  feet.  One  of  the  seams  in  the 
district  of  St.  Etienne  varies  from  30  to  70  feet 
thick,  whilst  the  fifteen  to  eighteen  workable 
seams  give  a  thickness  of  112  feet,  although  the 
total  area  of  the  field  is  not  great.  Again,  in  the 
remarkable  basin  of  the  Saone-et-Loire,  although 
there  are  but  ten  beds  of  coal,  two  of  them  run 
from  30  to  60  feet  each,  whilst  at  Creusot  the 
main  seam  actually  runs  locally  to  a  thickness 
varying  between  40  and  130  feet. 

The  Belgian  coal-field  stretches  in  the  form  of 
a  narrow  strip  from  7  to  9  miles  wide  by  about 
100  miles  long,  and  is  divided  into  three  prin- 
cipal basins.  In  that  stretching  from  Liege  to 
Verviers  there  are  eighty-three  seams  of  coal, 
none  of  which  are  less  than  3  feet  thick.  In  the 
basin  of  the  Sambre,  stretching  from  Namur  to 
Charleroi,  there  are  seventy-three  seams  which 
are  workable,  wrhilst  in  that  between  Mons  and 
Thulin  there  are  no  less  than  one  hundred  and 
fifty-seven  seams.  The  measures  here  are  so 
folded  in  zigzag  fashion,  that  in  boring  in  the 
neighbourhood  of  Mons  to  a  depth  of  350  yards 
vertical,  a  single  seam  was  passed  through  no 
less  than  six  times. 

Germany,  on  the  west  side  of  the  Rhine,  is 
excepticmally  fortunate  in  the  possession  of  the 
famous  Pfalz-Saarbrticken  coal-field,  measuring 
about  60  miles  long  by  20  miles  wide,  and  cover- 
ing about  175  square  miles.  Much  of  the  coal 
which  lies  deep  in  these  coal-measures  will  always 
remain  unattainable,  owing  to  the  enormous 
thickness  of  the  strata,  but  a  careful  computation 


THE   COAL  SUPPLIES   OF  THE  WORLD.        143 

made  of  the  coal  which  can  be  worked,  gives  an 
estimate  of  no  less  than  2750  millions  of  tons. 
There  is  a  grand  total  of  two  hundred  and  forty- 
four  seams,  although  about  half  of  them  are  un- 
workable. 

Beside  other  smaller  coal-producing  areas  in 
Germany,  the  coal-fields  of  Silesia  in  the  south- 
eastern corner  of  Prussia  are  a  possession  un- 
rivalled both  on  account  of  their  extent  and 
thickness.  It  is  stated  that  there  exist  333  feet 
of  coal,  all  the  seams  of  which  exceed  2-J-  feet, 
and  that  in  the  aggregate  there  is  here,  within  a 
workable  depth,  the  scarcely  conceivable  quantity 
of  50,000  million  tons  of  coal. 

The  coal-field  of  Upper  Silesia,  occupying  an 
area  about  20  miles  long  by  15  miles  broad,  is 
estimated  to  contain  some  10,000  feet  of  strata, 
with  333  feet  of  good  coal.  This  is  about  three 
times  the  thickness  contained  in  the  South  Wales 
coal-field,  in  a  similiar  thickness  of  coal-measures. 
There  are  single  seams  up  to  60  feet  thick,  but 
much  of  the  coal  is  covered  by  more  recent  rocks 
of  New  Red  and  Cretaceous  age.  In  Lower 
Silesia  there  are  numerous  seams  3^  feet  to  5  feet 
thick,  but  owing  to  their  liability  to  change  in 
character  even  in  the  same  seam,  their  value  is 
inferior  to  the  coals  of  Upper  Silesia. 

When  British  supplies  are  at  length  exhausted, 
it  is  anticipated  that  some  of  the  earliest  coals  to 
be  imported,  should  coal  then  be  needed,  will 
reach  Britain  from  the  upper  waters  of  the  Oder. 

The  coal-field  of  Westphalia  has  lately  come 
into  prominence  in  connection  with  the  search 
which  has  been  made  for  coal  in  Kent  and  Surrey, 
the  strata  which  are  mined  at  Dortmund  being 
thought  to  be  continuous  from  the  Bristol  coal- 


144          THE  STORY  OF  A  PIECE  OF  COAL. 

field.  Borings  have  been  made  through  the  chalk 
of  the  district  north  of  the  Westphalian  coal-field, 
and  these  have  shown  the  existence  of  further 
coal-measures.  The  coal-fields  extends  between 
Essen  and  Dortmund  a  distance  of  30  miles  east 
and  west,  and  exhibits  a  series  of  about  one  hun- 
dred and  thirty  seams,  with  an  aggregate  of  300 
feet  of  coal. 

It  is  estimated  that  this  coal-field  alone  con- 
tains no  less  than  39,200  millions  of  tons  of  coal. 

Russia  possesses  supplies  of  coal  whose  in- 
fluence has  scarcely  yet  been  felt,  owing  to  the 
sparseness  of  the  population  and  the  abundance 
of  forest.  Carboniferous  rocks  abut  against  the 
flanks  of  the  Ural  Mountains,  along  the  sides  of 
which  they  extend  for  a  length  of  about  a  thou- 
sand miles,  with  inter-stratifications  of  coal. 
Their  actual  contents  have  not  yet  been  gauged, 
but  there  is  every  reason  to  believe  that  those 
coal-beds  which  have  been  seen  are  but  samples 
of  many  others  which  will,  when  properly  worked, 
satisfy  the  needs  of  a  much  larger  population  than 
the  country  now  possesses. 

Like  the  lower  coals  of  Scotland,  the  Russian 
coals  are  found  in  the  carboniferous  limestone. 
This  may  also  be  said  of  the  coal-fields  in  the 
governments  of  Tula  and  Kaluga,  and  of  those  im- 
portant coal-bearing  strata  near  the  river  Donetz, 
stretching  to  the  northern  corner  of  the  Sea  of 
Azov.  In  the  last-named  the  seams  are  spread 
over  an  area  of  11,000  square  miles,  in  which 
there  are  forty-four  workable  seams  containing 
114  feet  of  coal.  The  thickest  of  known  Rus- 
sian coals  occur  at  Lithwinsk,  where  three  seams 
are  worked,  each  measuring  30  feet  to  40  feet 
thick. 


THE   COAL  SUPPLIES   OF  THE  WORLD.       145 

An  extension  of  the  Upper  Silesian  coal-field 
appears  in  Russian  Poland.  This  is  of  upper 
Carboniferous  age,  and  contains  an  aggregate  of 
60  feet  of  coal. 

At  Ostrau,  in  Upper  Silesia  (Austria),  there  is 
a  remarkable  coal-field.  Of  its  370  seams  there 
are  no  less  than  117  workable  ones,  and  these 
contain  350  feet  of  coal.  The  coals  here  are  very 
full  of  gas,  which  even  percolates  to  the  cellars  of 
houses  in  the  town.  A  bore  hole  which  was  sunk 
in  1852  to  a  depth  of  150  feet,  gave  off  a  stream 
of  gas,  which  ignited,  and  burnt  for  many  years 
with  a  flame  some  feet  long. 

The  Zwickau  coal-field  in  Saxony  is  one  of 
the  most  important  in  Europe.  It  contains  a  re- 
markable seam  of  coal,  known  as  Russokohle  or 
soot-coal,  running  at  times  25  feet  thick.  It  was 
separated  by  Geinitz  and  others  into  four  zones, 
according  to  their  vegetable  contents,  viz. : — 

1.  Zone  of  Ferns. 

2.  Zone  of  Annularia  and  Calamites. 

3.  Zone  of  Sigillaria. 

4.  Zone  of  Sagenaria  (in   Silesia),  equivalent 

to  the  culm-measures  of  Devonshire. 

Coals  belonging  to  other  than  true  Carbon- 
iferous age  are  found  in  Europe  at  Steyerdorf  on 
the  Danube,  where  there  are  a  few  seams  of  good 
coal  in  strata  of  Liassic  age,  and  in  Hungary  and 
Styria,  where  there  are  tertiary  coals  which  ap- 
proach closely  to  those  of  true  Carboniferous  age 
in  composition  and  quality. 

In  grjain  there  are  a  few  small  scattered  ba- 
sins. Coal-is  found  overlying  the  carboniferous 
limestone  of  the  Cantabrian  chain,  the  seams 
10 


146  THE   STORY  OF  A   PIECE   OF   COAL. 

being  from  5  feet  to  8  feet  thick.  In  the  Satero- 
valley,  near  Sotillo,  is  a  single  seam  measuring 
from  60  feet  to  100  feet  thick.  Coal  of  Neoco- 
mian  age  appears  at  Montalban. 

When  we  look  outside  the  continent  of  Eu- 
rope, we  may  well  be  astonished  at  the  bountiful 
manner  in  which  nature  has  laid  out  beds  of  coal 
upon  these  ancient  surfaces  of  our  globe. 

Professor  Rogers  estimated  that,  in  the  United 
States  of  America,  the  coal-fields  occupy  an  area 
of  no  less  than  196,850  square  miles. 

Here,  again,  it  is  extremely  probable  that  the 
coal-fields  which  remain,  in  spite  of  their  gigantic 
existing  areas,  are  but  the  remnants  of  one  tre- 
mendous area  of  deposit,  bounded  only  on  the 
east  by  the  Atlantic,  and  on  the  west  by  a  line 
running  from  the  great  lakes  to  the  frontiers 
of  Mexico.  The  whole  area  has  been  subjected 
to  forces  which  have  produced  foldings  and 
flexures  in  the  Carboniferous  strata  after  depo- 
sition. These  undulations  are  -greatest  near  the 
Alleghanies,  and  between  these  mountains  and  the 
Atlantic,  whilst  the  flexures  gradually  dying  out 
westward,  cause  the  strata  there  to  remain  fairly 
horizontal.  In  the  troughs  of  the  foldings  thus 
formed  the  coal-measures  rest,  those  portions 
which  had  been  thrown  up  as  anticlines  having 
suffered  loss  by  denudation.  Where  the  foldings 
are  greatest  there  the  coal  has  been  naturally 
most  altered;  bituminous  and  caking-coals  are 
characteristic  of  the  broad  flat  areas  west  of  the 
mountains,  whilst,  where  the  contortions  are 
greatest,  the  coal  becomes  a  pure  anthracite. 

It  must  not  be  thought  that  in  this  huge  area 
the  coal  is  all  uniformly  good.  It  varies  greatly 
in  quality,  and  in  some  districts  it  occurs  in  such 


THE  COAL  SUPPLIES  OF  THE  WORLD.       ^7 

thin  seams  as  to  be  worthless,  except  as  fuel  for 
consumption  by  the  actual  coal-getters.  There 
are,  too,  areas  of  many  square  miles  in  extent, 
where  there  are  now  no  coals  at  all,  the  forma- 
tion having  been  denuded  right  down  to  the 
palaeozoic  back-bone  of  the  country. 

The  chief  of  the  actual  coal-fields  is  that  of 
Pennsylvania.  The  output  of  anthracite  here  ex- 
ceeds that  of  bituminous  coal,  and  it  is  estimated 
that  the  supply  will  last  between  100  and  150 
years  longer.  The  great  field  of  which  this  is  a 
portion,  extends  in  an  unbroken  length  for  875 
miles  N.  E.  and  S.  W.,  and  includes  the  basins  of 
Ohio,  Maryland,  Virginia,  Kentucky,  and  Tennes- 
see. The  workable  seams  of  anthracite  about 
Pottsville  measure  in  the  aggregate  from  70  to 
207  feet.  Some  of  the  lower  seams  individually 
attain  an  exceptional  thickness,  that  at  Lehigh 
Summit  mine  containing  a  seam,  or  rather  a  bed, 
of  30  feet  of  good  coal. 

The  remarkable  Pittsburg  Seam  of  bituminous 
coal  is  8  feet  thick  at  its  outcrop  near  the  city  of 
Pittsburg,  whence  it  takes  its  name,  and  although 
its  thickness  varies  considerably,  Professor  Rogers 
estimated  that  the  sheet  of  coal  measures  super- 
ficially about  14,000  square  miles.  What  a  forest 
there  must  have  existed  to  produce  so  widespread 
a  bed!  Even  as  it  is,  it  has  at  a  former  epoch 
suffered  great  denudation,  if  certain  detached 
basins  should  be  considered  as  indicating  its  for- 
mer extent. 

The  principal  seam  in  the  anthracite  district 
of  central  Pennsylvania,  which  extends  for  about 
650  miles  along  the  left  bank  of  the  Susque- 
hanna,  is  known  as  the  "  Mammoth  "  vein,  and 
is  29^  feet  thick  at  Wilkesbarre,  whilst  at 


148          THE  STORY  OF  A   PIECE  OF  COAL. 

other  places  it  attains  to,  and  even  exceeds,  60 
feet. 

On  the  west  of  the  chain  of  mountains  the 
foldings  become  gentler,  and  the  coal  assumes  an 
almost  horizontal  position.  In  passing  through 
Ohio  we  find  a  saddle-back  ridge  or  anticline  of 
more  ancient  strata  than  the  coal,  and  in  con- 
sequence of  this,  we  have  a  physical  boundary 
placed  upon  the  coal-fields  on  each  side. 

Passing  across  this  older  ridge  of  denuded 
Silurian  and  other  rocks,  we  reach  the  famous  Illi- 
nois and  Indiana  coal-field,  whose  coal-measures 
lie  in  a  broad  trough,  bounded  on  the  west  by 
the  uprising  of  the  carboniferous  limestone  of 
the  Upper  Mississippi.  This  limestone  forma- 
tion appears  here  for  the  first  time,  having  been 
absent  on  the  eastern  side  of  the  Ohio  anticline. 
The  area  of  the  coal-field  is  estimated  at  51,000 
square  miles. 

In  connection  with  the  coal-fields  of  the  United 
States,  it  is  interesting  to  notice  that  a  wide  area 
in  Texas,  estimated  at  3000  square  miles,  pro- 
duces a  large  amount  of  coal  annually  from 
strata  of  the  Liassic  age.  Another  important  area 
of  production  in  eastern  Virginia  contains  coal 
referable  to  the  Jurassic  age,  and  is  similar  in 
fossil  contents  to  the  Jurassic  of  Whitby  and 
Brora.  The  main  seam  in  eastern  Virginia 
boasts  a  thickness  of  from  30  to  40  feet  of  good 
coal. 

Very  serviceable  lignites  of  Cretaceous  age 
are  found  on  the  Pacific  slope,  to  which  age  those 
of  Vancouver's  Island  and  Saskatchewan  River 
are  referable. 

Other  coal-fields  of  less  importance  are  found 
between  Lakes  Huron  and  Erie,  where  the  meas- 


THE  COAL  SUPPLIES  OF  THE   WORLD.        149 

ures  cover  an  area  of  5000  square  miles,  and  also 
in  Rhode  Island. 

In  British  North  America  we  find  extensive 
deposits  of  valuable  coal-measures.  Large  de- 
velopments occur  in  New  Brunswick  and  Nova 
Scotia.  At  South  Joggins  there  is  a  thickness  of 
14,750  feet  of  strata,  in  which  are  found  seventy- 
six  coal-seams  of  45  feet  in  total  thickness.  At 
Pictou  there  are  six  seams  with  a  total  of  80  feet 
of  coal.  In  the  lower  carboniferous  group  is 
found  the  peculiar  asphaltic  coal  of  the  Albert 
mine  in  New  Brunswick.  Extensive  deposits  of 
lignite  are  met  with  both  in  the  Dominion  and  in 
the  United  States,  whilst  true  coal-measures 
flank  both  sides  of  the  Rocky  Mountains.  Coal- 
seams  are  often  encountered  in  the  Arctic  archi- 
pelago. 

The  principal  areas  of  deposit  in  South  Ameri- 
ca are  in  Brazil,  Uruguay,  and  Peru.  The  largest 
is  the  Candiota  coal-field,  in  Brazil,  where  sec- 
tions in  the  valley  of  the  Candiota  River  show 
five  good  seams  with  a  total  of  65  feet  of  coal. 
It  is,  however,  worked  but  little,  the  principal 
workings  being  at  San  Jeronimo  on  the  Jacaha- 
hay  River. 

In  Peru  the  true  carboniferous  coal-seams  are 
found  on  the  higher  ground  of  the  Andes,  whilst 
coal  of  secondary  age  is  found  in  considerable 
quantities  on  the  rise  towards  the  mountains. 
At  Porton,  east  of  Truxillo,  the  same  meta- 
morphism  which  has  changed  the  ridge  of  sand- 
stone to  a  hard  quartzite  has  also  changed  the 
ordinary  bituminous  coal  into  an  anthracite, 
which  is  here  vertical  in  position.  The  coals  of 
Peru  usually  rise  to  more  than  10,000  feet  above 
the  sea,  and  they  are  practically  inaccessible. 


150  THE  STORY  OF  A   PIECE  OF  COAL. 

Cretaceous  coals  have  been  found  at  Lota  in 
Chili,  and  at  Sandy  Point,  Straits  of  Magellan. 

Turning  to  Asia,  we  find  that  coal  has  been 
worked  from  time  to  time  at  Heraclea  in  Asia 
Minor.  Lignites  are  met  with  at  Smyrna  and 
Lebanon. 

The  coal-fields  of  Hindustan  are  small  but 
numerous,  being  found  in  all  parts  of  the  penin- 
sula. There  is  an  important  coal-field  at  Rani- 
ganj,  near  the  Hooghly,  140  miles  north  of  Cal- 
cutta. It  has  an  area  of  500  square  miles.  In 
the  Raniganj  district  there  are  occasional  seems 
20  feet  to  80  feet  in  thickness,  but  the  coals  are 
of  somewhat  inferior  quality. 

The  best  quality  amongst  Indian  coals  has 
come  from  a  small  coal-field  of  about  n  square 
miles  in  extent,  situated  at  Kurhurbali  on  the 
East  Indian  Railway.  Other  coal-fields  are  found 
at  Jherria  and  on  the  Sone  River,  in  Bengal,  and 
at  Mopani  on  the  Nerbudda.  Much  is  expected 
in  future  from  the  large  coal-field  of  the  Wardha 
and  Chanda  districts,  in  the  Central  Provinces, 
the  coal  of  which  may  eventually  prove  to  be  of 
Permian  age. 

The  coal-deposits  of  Chjjia  are  undoubtedly 
of  tremendous  extent,  although  from  want  of  ex- 
ploration it  is  difficult  to  form  any  satisfactory 
estimate  of  them.  Near  Pekin  there  are  beds  of 
coal  95  feet  thick,  which  afford  ample  provision 
for  the  needs  of  the  city.  In  the  mountainous 
districts  of  western  China  the  area  over  which 
carboniferous  strata  are  exposed  has  been  esti- 
mated at  100,000  square  miles.  The  coal-measures 
extend  westward  to  the  Mongolian  frontier, 
where  coal-seams  30  feet  thick  are  known  to  lie 
in  horizontal  plane  for  200  miles.  Most  of  the 


THE   COAL   SUPPLIES  OF  THE  WORLD.       151 

Chinese  coal-deposits  are  rendered  of  small  value, 
either  owing  to  the  mountainous  nature  of  the 
valleys  in  which  they  outcrop,  or  to  their  inac- 
cessibility from  the  sea.  Japan  is  not  lacking  in 
good  supplies  of  coal.  A  colliery  is  worked  by 
the  government  on  the  island  of  Takasima,  near 
Nagasaki,  for  the  supply  of  coals  for  the  use  of 
the  navy. 

The  British  possession  of  Labuan,  off  the  island 
of  Borneo,  is  rich  in  a  coal  of  tertiary  age,  remark- 
able for  the  quantity  of  fossil  resin  which  it  con- 
tains. Coal  is  also  found  in  Sumatra,  and  in  the 
Malayan  Archipelago. 

In  Cape  Colony  and  Natal  the  coal-bearing 
Karoo  beds  are  probably  of  New  Red  age.  The 
coal  is  reported  to  be  excellent  in  quantity. 

In  Abyssinia  lignites  are  frequently  met  with 
in  the  high  lands  of  the  interior. 

Coal  is  very  extensively  developed  throughout 
Australasia.  In  New  South  Wales,  coal-measures 
occur  in  large  detached  portions  between  29°  and 
35°  S.  latitude.  The  Newcastle  district,  at  the 
mouth  of  the  Hunter  river,  is  the  chief  seat  of 
the  coal  trade,  and  the  seams  are  here  found  up 
to  30  feet  thick.  Coal-bearing  strata  are  found 
at  Rowen  River,  in  Queensland,  covering  an  area 
of  24,000  square  miles,  whilst  important  mines  of 
Cretaceous  age  are  worked  at  Ipswich,  near  Bris- 
bane. In  New  Zealand  quantities  of  lignite,  de- 
scribed as  a  hydrous  coal,  are  found  and  utilised ; 
also  an  anhydrous  coal  which  may  prove  to  be 
either  of  Cretaceous  or  Jurassic  age. 

We  have  thus  briefly  sketched  the  supplies  of 
coal,  so  far  as  they  are  known,  which  are  to  be 
found  in  various  countries.  But  England  has  of 
late  years  been  concerned  as  to  the  possible  fail- 


152  THE  STORY  OF  A  PIECE  OF   COAL. 

tire,  of  her  home  supplies  in  the  not  very  distant 
future,  and  the  effects  which  such  failure  would 
be  likely  to  produce  on  the  commercial  prosperity 
of  the  country. 

/  Great  Britain  has  long  been  the  centre  of  the 
/universe  in  the  supply  of  the  world's  coal,  and  as 
a  matter  of  fact,  has  been  for  many  years  raising 
considerably  more  than  one  half  of  the  total 
amount  of  coal  raised  throughout  the  whole 
world.  There  is,  as  we  have  seen,  an  abundance 
of  coal  elsewhere,  which  will,  in  the  course  of 
time,  compete  with  her  when  properly  worked, 
but  Britain  seems  to  have  early  taken  the  lead  in 
the  production  of  coal,  and  to  have  become  the 
great  universal  coal  distributor.  Those  who  have 
misgivings  as  to  what  will  happen  when  her  coal 
is  exhausted,  receive  little  comfort  from  the  fact 
that  in  North  America,  in  Prussia,  in  China  and 
elsewhere,  there  are  tremendous  supplies  of  coal 
as  yet  untouched,  although  a  certain  sense  of  re- 
lief is  experienced  when  that  fact  becomes  gener- 
ally known. 

If  by  the  time  of  exhaustion  of  the  home 
mines  Britain  is  still  dependent  upon  coal  for 
fuel,  which,  in  this  age  of  electricity,  scarcely 
seems  probable,  her  trade  and  commerce  will  feel 
with  tremendous  effect  the  blow  which  her  pres- 
tige will  experience  when  the  first  vessel,  laden 
with  foreign  coal,  weighs  anchor  in  a  British  har- 
bour. In  the  great  coal  lock-out  of  1893,  when, 
for  the  greater  part  of  sixteen  weeks,  scarcely  a 
ton  of  coal  reached  the  surface  in  some  of  her 
principal  coal-fields,  it  was  rumoured,  falsely  as 
it  appeared,  that  a  collier  from  America  had  in- 
deed reached  those  shores,  and  the  importance 
which  attached  to  the  supposed  event  was  shown 


THE  COAL  SUPPLIES  OF  THE  WORLD.       153 

by  the  anxious  references  to  it  in  the  public  press, 
where  the  truth  or  otherwise  of  the  alarm  was 
actively  discussed.  Should  such  a  thing  at  any 
time  actually  come  to  pass,  it  will  indeed  be  a 
retribution  to  those  who  have  for  years  been 
squandering  their  inheritance  in  many  a  wasteful 
manner  of  coal-consumption. 

Thirty  years  ago,  when  so  much  small  coal 
was  wasted  and  wantonly  consumed  in  order  to 
dispose  of  it  in  the  easiest  manner  possible^at  the 
pit-mouths,  and  when  only  the  best  and  largest 
coal  was  deemed  to  be  of  any  value,  louder  and 
louder  did  scientific  men  speak  in  protest  against 
this  great  and  increasing  prodigality.  Wild  esti- 
mates were  set  on  foot  showing  how  that,  sooner 
or  later,  there  would  be  in  Britain  no  native  sup- 
ply of  coal  at  all,  and  finally  a  Royal  Commission 
was  appointed  in  1866,  to  collect  evidence  and 
report  upon  the  probable  time  during  which  the 
supplies  of  Great  Britain  would  last. 

This  Commission  reported  in  1871,  and  the 
outcome  of  it  was  that  a  period  of  twelve  hun- 
dred and  seventy-three  years  was  assigned  as  the 
period  during  which  the  coal  would  last,  at  the 
then-existing  rate  of  consumption.  The  quantity 
of  workable  coal  within  a  depth  of  4000  feet  was 
estimated  to  be  90,207  millions  of  tons,  or,  in- 
cluding that  at  greater  depths,  146,480  millions 
of  tons.  Since  that  date,  however,  there  has  been 
a  steady  annual  increase  in  the  amount  of  coal 
consumed,  and  subsequent  estimates  go  to  show 
that  the  supplies  cannot  last  for  more  than  250 
years,  or,  taking  into  consideration  a  possible 
decrease  in  consumption,  350  years.  Most  of  the 
coal-mines  will,  indeed,  have  been  worked  out  in 
less  than  a  hundred  years  hence,  and  then,  per- 


154  THE   STORY  OF  A   PIECE   OF  COAL. 

haps,  the  competition  brought  about  by  the  de- 
mand for,  and  the  scarcity  of,  coal  from  the  re- 
maining mines,  will  have  resulted  in  the  dreaded 
importation  of  coal  from  abroad. 

In  referring  to  the  outcome  of  the  Royal 
Commission  of  1866,  although  the  Commissioners 
fixed  so  comparatively  short  a  period  as  the 
probable  duration  of  the  coal  supplies,  it  is  but 
fair  that  it  should  be  stated  that  other  estimates 
have  been  made  which  have  materially  differed 
from  their  estimate.  Whereas  one  estimate  more 
than  doubled  that  of  the  Royal  Commission,  that 
of  Sir  William  Armstrong  in  1863  gave  it  as  212 
years,  and  Professor  Jevons,  speaking  in  1875 
concerning  Armstrong's  estimate,  observed  that 
the  annual  increase  in  the  amount  used,  %hich 
was  allowed  for  in  the  estimate,  had  so  greatly 
itself  increased,  that  the  212  years  must  be  con- 
siderably reduced. 

One  can  scarcely  thoroughly  appreciate  the 
enormous  quantity  of  coal  that  is  brought  to  the 
surface  annually,  and  the  only  wonder  is  that 
there  are  any  supplies  left  at  all.  The  Great 
Pyramid,  which  is  said  by  Herodotus  to  have 
been  twenty  years  in  building,  and  which  took 
100,000  men  to  build,  contains  3,394,307  cubic 
yards  of  stone.  The  coal  raised  in  1892  would 
make  a  pyramid  which  would  contain  181,500,000 
cubic  yards,  at  the  low  estimate  that  one  ton 
could  be  squeezed  into  one  cubic  yard. 

The  increase  in  the  quantity  of  coal  which  has 
been  faised  in  succeeding  years  can  well  be  seen 
from  the  following  facts. 

In  1820  there  were  raised  in  Great  Britain 
about  20  millions  of  tons.  By  1855  this  amount 
had  increased  to  64^  millions.  In  1865  this  again 


THE   COAL-TAR   COLOURS.  155 

had  increased  to  98  millions,  whilst  twenty  years 
after,  viz.,  in  1885,  this  had  increased  to  no  less 
than  159  millions,  such  were  the  giant  strides 
which  the  increase  in  consumption  made. 

In  the  return  for  1892,  this  amount  had  farther 
increased  to  181^-  millions  of  tons,  an  advance  in 
eight  years  of  a  quantity  more  than  equal  to  the 
total  raised  in  1820,  and  in  1894  the  total  reached 
199^  millions;  this  was  produced  by  795,240  per- 
sor-s,  employed  in  and  about  the  mines. 


CHAPTER  VIII. 

THE    COAL-TAR    COLOURS. 

IN  a  former  chapter  some  slight  reference  has 
been  made  to  those  bye-products  of  coal-tar  which 
have  proved  so  valuable  in  the  production  of  the 
aniline  dyes.  It  is  thought  that  the  subject  is  of 
so  interesting  a  nature  as  to  deserve  more  notice 
than  it  was  possible  to  bestow  upon  it  in  that 
place.  With  abstruse  chemical  formulae  and  com- 
plex chemical  equations  it  is  proposed  to  have  as 
little  as  possible  to  do,  but  even  the  most  unscien- 
tific treatment  of  the  subject  must  occasionally 
necessitate  a  scientific  method  of  elucidation. 

The  dyeing  industry  has  been  radically  changed 
during  the  last  half  century  by  the  introduction  of 
what  are  known  as  the  artificial  dyes,  whilst  the 
^natural  colouring  matters  which  had  previously 
been  the  sole  basis  of  the  industry,  and  which  had 
been  obtained  by  very  simple  chemical  methods 
from  some  of  the  constituents  of  the  animal  king- 
dom, or  which  were  found  in  a  natural  state  in 


156  THE   STORY   OF  A   PIECE   OF   COAL. 

the  vegetable  kingdom,  have  very  largely  given 
place  to  those  which  have  been  obtained  from 
coal-tar,  a  product  of  the  mineralised  vegetation 
of  the  carboniferous  age. 

The  development  and  discovery  of  the  aniline 
colouring  matters  were  not,  of  course, 'possible 
until  after  the  extensive  adoption  of  house-gas 
for  illuminating  purposes,  and  even  then  it  wras 
many  years  before  the  waste  products  from  the 
gas-works  came  to  have  an  appreciable  value  of 
their  own.  This,  however,  came  with  the  in- 
creased utilitarianism  of  the  commerce  of  the 
present  century,  but  although  aniline  was  first 
discovered  in  1826  by  Unverdorben,  in  the 
materials  produced  by  the  dry  distillation  of 
indigo  (Portuguese,  anil,  indigo),  it  wras  not  un- 
til thirty  years  afterwards,  namely,  in  1856,  that 
the  discovery  of  the  method  of  manufacture  of 
the  first  aniline  dye,  mauveine,  was  announced, 
the  discovery  being  due  to  the  persistent  efforts 
of  Perkin,  to  whom,  together  with  other  chemists 
working  in  the  same  field,  is  due  the  great  ad- 
vance which  has  been  made  in  the  chemical 
knowledge  of  the  carbon,  hydrogen,  and  oxygen 
compounds.  Scientists  appeared  to  work  along 
two  planes ;  there  were  those  who  discovered 
certain  chemical  compounds  in  the  resulting  pro- 
ducts of  reactions  in  the  treatment  of  existing 
vegetation,  and  there  were  those  who,  studying 
the  wonderful  constituents  in  coal-tar,  the  pro- 
duct of  a  past  age,  immediately  set  to  work  to 
find  therein  those  compounds  which  their  con- 
temporaries had  already  discovered.  Generally, 
too,  with  signal  success. 

The  discovery  of  benzene  in  1825  by  Faraday 
was  followed  in  the  course  of  a  few  years  by  its 


THE  COAL-TAR  COLOURS. 


157 


discovery  in  coal-tar  by  Hofmann.  Toluene, 
which  was  discovered  in  1837  by  Pelletier,  was 
recognised  in  the  fractional  distillation  of  crude 
naphtha  by  Mansfield  in  1848.  Although  the 
method  of  production  of  mauveine  on  a  large 
scale  was  not  accomplished  until  1856,  yet  it  had 
been  noticed  in  1834,  the  actual  year  of  its  recog- 
nition as  a  constituent  of  coal-tar,  that,  when 
brought  into  contact  with  chloride  of  lime,  it 
gave  brilliant  colours,  but  it  required  a  consider- 
able cheapening  of  the  process  of  aniline  manu- 
facture before  the  dyes  commenced  to  enter  into 
competition  with  the  old  natural  dyes. 

The  isolation  of  aniline  from  coal-tar  is  ex- 
pensive, in  consequence  of  the  small  quantities  in 
which  it  is  there  found,  but  it  was  discovered  by 
Mitscherlich  that  by  acting  upon  benzene,  one  of 
the  early  distillates  of  coal-tar,  for  the  production 
of  nitrobenzole,  a  compound  was  produced  from 
which  aniline  could  be  obtained  in  targe  quanti- 
ties-. There  were  thus  two  methods  of  obtain- 
ing aniline  from  tar,  the  experimental  and  the 
practical. 

In  producing  nitrobenzole  (nitrobenzene), 
chemically  represented  as  C6H5NO2,  the  nitric 
acid  used  as  the  reagent  with  benzene,  is  mixed 
with  a  quantity  of  sulphuric  acid,  with  the  object 
of  absorbing  water  which  is  formed  during  the 
reaction,  as  this  would  tend  to  dilute  the  efficien- 
cy of  the  nitric  acid.  The  proportions  are  100 
parts  of  purified  benzene,  with  a  mixture  of  115 
parts  of  concentrated  nitric  acid  (HNO3),  and 
160  parts  of  concentrated  sulphuric  acid.  The 
mixture  is  gradually  introduced  into  the  large 
cast-iron  cylinder  into  which  the  benzene  has  been 
poured.  The  outside  of  the  cylinder  is  supplied 


158  THE  STORY  OF  A   PIECE  OF   COAL. 

with  an  arrangement  by  which  fine  jets  of  water 
can  be  made  to  play  upon  it  in  the  early  stages 
of  the  reaction  which  follows,  and  at  the  end  of 
from  eight  to  ten  hours  the  contents  are  allowed 
to  run  off  into  a  storage  reservoir.  Here  they 
arrange  themselves  into  two  layers,  the  top  of 
which  consists  of  the  nitrobenzene  which  has 
been  produced,  together  with  some  benzene  which 
is  still  unacted  upon.  The  mixture  is  then  freed 
from  the  latter  by  treatment  with  a  current  of 
steam.  Nitrobenzene  presents  itself  as  a  yellow- 
ish oily  liquid  ,  with  a  pecular  taste  as  of  bit- 
ter almonds.  It  was  formerly  in  great  demand 
by  perfumers,  but  its  poisonous  properties  render 
it  a  dangerous  substance  to  deal  with.  In  prac- 
tice a  given  quantity  of  benzene  will  yield  about 
150  per  cent,  of  nitrobenzene.  Stated  chem- 
ically, the  reaction  is  shown  by  the  following 
equation  : — 

C6H6     -f      HNO3   =       C6H5NO2     +    H3O 
(Benzene)   (Nitric  acid)   (Nitrobenzene)  (Water). 

The  water  which  is  thus  formed  in  the  process, 
by  the  freeing  of  one  of  the  atoms  of  hydrogen 
in  the  benzene,  is  absorbed  by  the  sulphuric  acid 
present,  although  the  latter  takes  no  actual  part 
in  the  reaction. 

From  the  nitrobenzene  thus  obtained,  the 
aniline  Which  is  now  used  so  extensively  is  pre- 
pared. The  component  atoms  of  a  molecule 
of  aniline  are  shown  in  the  formula  C6H5NH2. 
It  is  also  known  as  phenylamine  or  amido-ben- 
zole,  or  commercially  as  aniline  oil.  There  are 
various  methods  of  reducing  nitrobenzene  for 
aniline,  the  object  being  to  replace  the  oxygen 


THE   COAL-TAR  COLOURS.  159 

of  the  former  by  an  equivalent  number  of  atoms 
of  hydrogen.  The  process  generally  used  is  that 
known  as  Bechamp's,  with  slight  modifications. 
Equal  volumes  of  nitrobenzene  and  acetic  acid, 
together  with  a  quantity  of  iron-filings  rather 
in  excess  of  the  weight  of  the  nitrobenzene,  are 
placed  in  a  capacious  retort.  A  brisk  efferves- 
cence ensues,  and  to  moderate  the  increase  of 
temperature  which  is  caused  by  the  reaction,  it  is 
found  necessary  to  cool  the  retort.  Instead  of 
acetic  acid  hydrochloric  acid  has  been  a  good 
deal  used,  with,  it  is  said,  certain  advantageous 
results.  From  60  to  65  per  cent,  of  aniline  on 
the  quantity  of  nitrobenzene  used,  is  yielded  by 
Bechamp's  process. 

Stated  in  a  few  words,  the  above  is  the  pro- 
cess adopted  on  all  hands  for  the  production  of 
commercial  aniline,  or  aniline  oil.  The  details 
of  the  distillation  and  rectification  of  the  oil  are, 
however,  as  varied  as  they  can  well  be,  no  two 
manufacturers  adopting  the  same  process.  Many 
of  the  aniline  dyes  depend  entirely  for  their 
superiority  on  the  qua44tyi-of--th^-oi4-ttsed,  and  for 
this  reason  it  is  subject  to  one  or  more  processes 
of  rectification.  This  is  performed  by  distilling, 
the  distillates  of  the  various  temperatures  being 
separately  collected. 

When  pure,  aniline  is  a  colourless  oily  liquid, 
but  on  exposure  rapidly  turns  brown.  It  has 
strong  refracting  powers  and  an  agreeable  aro- 
matic smell.  It  is  very  poisonous  when  taken  in- 
ternally ;  its  sulphate  is,  however,  sometimes  used 
medicinally.  It  is  by  the  action  upon  aniline  of 
certain  oxidising  agents,  that  the  various  colour- 
ing matters  so  well  known  as  aniline  dyes  are 
obtained. 


160          THE  STORY  OF  A   PIECE  OF  COAL. 

Commercial  aniline  oil  is  not,  as  we  have  seen, 
the  purest  form  of  rectified  aniline.  The  aniline 
oils  of  commerce  are  very  variable  in  character, 
the  principal  constituents  being  pure  aniline,  para- 
and  meta-toluidine,  xylidines,  and  cumidines. 
They  are  best  known  to  the  colour  manufacturer 
in  four  qualities — 

a)  Aniline  oil  for  blue  and  black. 

b)  Aniline  oil  for  magenta. 
Aniline  oil  for  safranine. 

d)  Liquid  toluidine. 

From  the  first  of  these,  which  is  almost  pure 
aniline,  aniline  black  is  derived,  and  a  number  of 
organic  compounds  which  are  further  used  for 
the  production  of  dyes.  The  hydrochloride  of 
aniline  is  important  and  is  known  commercially 
as  "  aniline  salt." 

The  distillation  and  rectification  of  aniline  oil 
is  practised  on  a  similar  principle  to  the  frac- 
tional distillation  which  we  have  noticed  as  being 
used  for  the  distillation  of  the  naphthas.  First, 
light  aniline  oils  pass  over,  followed  by  others, 
and  finally  by  the  heavy  oils,  or  "  aniline-tailings." 
It  is  a  matter  of  great  necessity  to  those  engaged 
in  colour  manufacture  to  apply  that  quality  of  oil 
which  is  best  for  the  production  of  the  colour  re- 
quired. This  is  not  always  an  easy  matter,  and 
there  is  great  divergence  in  opinion  and  prac- 
tice on  these  points. 

The  so-called  aniline  colours  are  not  all  derived 
from  aniline,  such  colouring  matters  being  in  some 
cases  derived  from  other  coal-tar  products,  such 
as  benzene  and  toluene,  phenol,  naphthalene,  and 
anthracene,  and  it  is  remarkable  that  although  the 


THE   COAL-TAR  COLOURS.  l6l 

earlier  dyes  were  produced  from  the  lighter  and 
more  easily  distilled  products  of  coal-tar,  yet  now 
some  of  the  heaviest  and  most  .stubborn  of  the 
distillates  are  brought  under  requisition  for  col- 
ouring matters,  those  which  not  many  years  ago 
were  regarded  as  fit  only  to  be  used  as  lubricants 
or  to  be  regarded  as  waste. 

It  is  scarcely  necessary  or  advisable  in  a  work 
of  this  kind  to  pursue  the  many  chemical  reac- 
tions, which,  from  the  various  acids  and  bases, 
result  ultimately  in  the  many  shades  and  grada- 
tions of  colour  which  are  to  be  seen  in  dress  and 
other  fabrics.  Many  of  them,  beautiful  in  the 
extreme,  are  the  outcome  of  much  careful  and 
well-planned  study,  and  to  print  here  the  com- 
plicated chemical  formulae  which  show  the  great 
changes  taken  place  in  compounds  of  complex 
molecules,  or  to  mention  even  the  names  of  these 
many-syllabled  compounds,  would  be  to  destroy 
the  purpose  of  this  little  book.  The  Rosanilines, 
the  Indulines,  and  Safranines  ;  the  Oxazines,  the 
Thionines :  the  Phenol  and  Azo  dyes  are  all  sub- 
stances which  are  of  greater  interest  to  the  chem- 
ical student  and  to  the  colour  manufacturer  than 
to  the  ordinary  reader.  Many  of  the  names  of 
the  bases  of  various  dyes  are  unknown  outside 
the  chemical  dyeworks,  although  each  and  all 
have  complicated  reactions  of  their  own.  In  the 
reds  are  rosanilines,  toluidine,  xylidine,  &c. ;  in  the 
blues — phenyl-rosanilines,  diphenylamine,  tolui- 
dine, aldehyde,  &c. ;  violets — rosaniline,  mauve, 
phenyl,  ethyl,  methyl,  &c.  ;  greens — iodine,  ani- 
line, leucaniline,  chrysotoluidine,  aldehyde,  tolui- 
dine, methyl-aniline,  &c.  ;  yellows  and  orange — 
leucaniline,  phenylamine,  &c.  ;  browns — chryso- 
toluidine, &c. ;  blacks — aniline,  toluidine,  &c. 
ii 


162  THE  STORY  OF  A   PIECE  OF  COAL. 

To  take  the  rosanilines  as  an  instance  of  the 
rest. 

Aniline  red,  magenta,  azaleine,  rubine,  solfer- 
ino,  fuchsine,  chryaline,  roseine,  erythrobenzine, 
and  others,  are  colouring  matters  in  this  group 
which  are  salts  of  rosaniline,  and  which  are  all 
recognised  in  commerce. 

The  base  rosaniline  is  known  chemically  by 
the  formula  C20H19N3,  and  is  prepared  by  heating 
a  mixture  of  magenta  aniline,  toluidine,  and 
pseudotoluidine,  with  arsenic  acid  and  other  oxi- 
dising agents.  It  is  important  that  water  should 
be  used  in  such  quantities  as  to  prevent  the  solu- 
tion of  arsenic  acid  from  depositing  crystals  on 
cooling.  Unless  carefully  crystallised  rosaniline 
will  contain  a  slight  proportion  of  the  arseniate, 
and  when  articles  of  clothing  are  dyed  with  the 
salt,  it  is  likely  to  produce  an  inflammatory  con- 
dition of  skin,  when  worn.  Some  years  ago  there 
was  a  great  outcry  against  hose  and  other  articles 
dyed  with  aniline  dyes,  owing  to  the  bad  effects 
which  were  produced,  and  this  has  no  doubt 
proved  very  prejudicial  to  aniline  dyes  as  a 
whole. 

Again,  the  base  known  as  mauve,  or  mauveine, 
has  a  composition  shown  by  the  formula  C27H24N4. 
It  is  produced  from  the  sulphate  of  aniline  by 
mixing  it  with  a  cold  saturated  solution  of  bi- 
chromate of  potash,  and  allowing  the  mixture  to 
stand  for  ten  or  twelve  hours.  A  blue-black  pre- 
cipitate is  then  formed,  which,  after  undergoing 
a  process  of  purification,  is  dissolved  in  alcohol 
and  evaporated  to  dryness.  A  metallic-looking 
powder  is  then  obtained,  which  constitutes  this 
all-important  base.  Mauve  forms  with  acids  a 
series  of  well-defined  salts  and  is  capable  of  ex- 


THE  COAL-TAR  COLOURS.  163 

pelling  ammonia  from  its  combinations.  Mauve  was 
the  first  aniline  dye  which  was  produced  on  a  large 
scale,  this  being  accomplished  by  Perkin  in  1856. 

The  substance  known  as  carbolic  acid  is  so 
useful  a  product  of  a  piece  of  coal  that  a  descrip- 
tion of  the  method  of  its  production  must  neces- 
sarily have  a  place  here.  It  is  one  of  the  most 
powerful  antiseptic  agents  with  which  we  are 
acquainted,  and  has  strong  anaesthetic  qualities. 
Some  useful  dyes  are  also  obtained  from  it.  It  is 
obtained  in  quantities  from  coal-tar,  that  portion 
of  the  distillate  known  as  the  heavy  oils  being  its 
immediate  source.  The  tar  oil  is  mixed  with  a 
solution  of  caustic  soda,  and  the  mixture  is  vio- 
lently agitated.  This  results  in  the  caustic  soda 
dissolving  out  the  carbolic  acid,  whilst  the  undis- 
solved  oils  collect  upon  the  surface,  allowing  the 
alkaline  solution  to  be  drawn  from  beneath.  The 
soda  in  the  solution  is  then  neutralised  by  the 
addition  of  a  suitable  quantity  of  sulphuric  acid, 
and  the  salt  so  formed  sinks  while  the  carbolic 
acid  rises  to  the  surface. 

Purification  of  the  product  is  afterwards  car- 
ried out  by  a  process  of  fractional  distillation. 
There  are  various  other  methods  of  preparing 
carbolic  acid. 

Carbolic  acid  is  known  chemically  as  C6H5(HO). 
When  pure  it  appears  as  colourless  needle-like 
crystals,  and  is  exceedingly  poisonous.  It  has 
been  used  with  marked  success  in  staying  the 
course  of  disease,  such  as  cholera  and  cattle 
plague.  It  is  of  a  very  volatile  nature,  and  its 
efficacy  lies  in  its  power  of  destroying  germs  as 
they  float  in  the  atmosphere.  Modern  science  tells 
us  that  all  diseases  have  their  origin  in  certain 
germs  which  are  everywhere  present  and  which 


164          THE  STORY  OF  A   PIECE  OF  COAL. 

seek  only  a  suitable  nidus  in  which  to  propogate 
and  flourish.  Unlike  mere  deodorisers  which 
simply  remove  noxious  gases  or  odours  ;  unlike 
disinfectants  which  prevent  the  spread  of  in- 
fection, carbolic  acid  strikes  at  the  very  root  and 
origin  of  disease  by  oxidising  and  consuming  the 
germs  which  breed  it.  So  powerful  is  it  that 
one  part  in  five  thousand  parts  of  flour  paste, 
blood,  &c.,  will  for  months  prevent  fermentation 
and  putrefaction,  whilst  a  little  of  its  vapour  in 
the  atmosphere  will  preserve  meat,  as  well  as 
prevent  it  from  becoming  fly-blown.  Although 
it  has,  in  certain  impure  states,  a  slightly  dis- 
agreeable odour,  this  is  never  such  as  to  be  in 
any  way  harmful,  whilst  on  the  other  hand  it  is 
said  to  act  as  a  tonic  to  those  connected  with  its 
preparation  and  use. 

The  new  artificial  colouring  matters  which  are 
continually  being  brought  into  the  market,  testify 
to  the  fact  that,  even  with  the  many  beautiful 
tints  and  hues  which  have  been  discovered, 
finality  and  perfection  have  not  yet  been  reached. 
A  good  deal  of  popular  prejudice  has  arisen 
against  certain  aniline  dyes  on  account  of  their 
inferiority  to  many  of  the  old  dye-stuffs  in  respect 
to  their  fastness,  but  in  recent  years  the  manu- 
facture of  many  which  were  under  this  disadvan- 
tage of  looseness  of  dye,  has  entirely  ceased, 
whilst  others  have  been  introduced  which  are 
quite  as  fast,  and  sometimes  even  faster  than  the 
natural  dyes. 

It  is  convenient  to  express  the  constituents  of 
coal-tar,  and  the  distillates  of  those  constituents, 
in  the  form  of  a  genealogical  chart,  and  thus,  by 
way  of  conclusion,  summarise  the  results  which 
we  have  noticed. 


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INDEX. 


A. 

Accidents,  causes  of  mining,  94. 

Age  of  A  crogens,  23. 

A  lethopteriS)  17. 

Alizarin,  137. 

American  coal-fields,  146. 

Ammoniacal  liquor,  137. 

Aniline,    136 ;    dyes,    156-161  ;    oil, 

159  ;  salt,  160  ;  tailings,  160. 
Anthracene,  128. 
Anthracite,  73,  74. 
Artificial  turpentine  oil,  127. 
Asphalt,  134. 
Australian  coals,  151. 
Aviculopecten,  62. 

B. 

Bechamp's  process,  159. 
Benzene,  126 ;  dangers,  127. 
Bind,  42. 

Bitumen  in  Trinidad,  135. 
Blower,  88. 
Boghead  coal,  129. 
Bog-oak,  69. 
Boring  diamonds,  81. 
Bovey  Tracey  lignite,  72. 
British  coal-fields,  140. 
British  North-American  coal-meas- 
ures, 149. 
Briquettes,  126. 

C. 

Calamites^  extinct  horsetails,  18. 

Carbolic  acid,  163. 

Carboniferous  formation,  the,  37. 

Cardiocarpum^  fossil  fruit,  34. 

Carelessness  of  miners,  95. 

Causes  of  earth-movements,  56. 
•  Changes  of  level,  50. 
1  Charcoal  as  a  disinfectant,  83. 

Chemistry  of  a  gas-flame,  115. 


Chinese  coals,  150. 
Clanny's  safety-lamp,  90. 
Clayton's  experiments  with  gas,  113. 
Clay,  regularity  in  deposition  of,  43. 
Club-mosses,  great  height  of  fossil, 

24. 
Coal,  vegetable  origin  of,  n  ;  formed 

by  escape  of  gases,  12  ;  not  the 

result  of  drifted  vegetation,  48  ; 

formed  in  large  lakes  or  closed 

seas,  52. 

Coal-dust,  danger  from,  98. 
Coal  formation,  geological  position 

of,  36. 

Coal-mine,  the;  84. 
Coal-period,  climate  of,  35. 
Coal-pipes,  94  97. 
Coal-plants,  classification  of,  22. 
Coal-seam,  each,  a  forest  growth,  40. 
Coals  of  non-carboniferous  age,  59. 
Coke,  139. 
Condensers,  118. 
Cones  of  Lepidodendra,  26. 
Conifers  in  coal-measures,  32. 
Current-bedding  in  sandstone,  39. 

D. 

Davy-lamp,  90. 

Darwin  on  the  Chonos  Archipela- 
go, 69. 

Diamonds,  how  made  artificially,  78. 

Disintegration  of  vegetable  sub- 
stances, 66. 

Disproportion  in  relative  thickness 
of  coal  and  coal-measures,  36. 

•  E. 

£arly  use  of  coal,  101. 
Encrinital  limestone,  46. 
Equiseta,  20. 
Essence  de  mirbane,  127. 
European  coal-fields,  141. 


166 


INDEX. 


l67 


Evelyn  on  the  use  of  coal,  106. 

Experiments  illustrating  fossilisa- 
tion,  18. 

Explosion,  first  record  of,  89  ;  ef- 
fects of  an,  93. 

F. 

Firedamp,  88,  89. 
Fire  in  mines,  93. 
First  light  oils,  125. 
Flashing- point  of  oil,  131. 
Flooding  of  pits,  94. 
Fog  and  smoke,  107. 
Foraminifera^  45. 
Fossil  ferns,  14. 

Fructification  on  fossil-ferns,  18. 
Furnace,  ventilating,  87. 

G. 
Gas,  coal,  in  ;  first  use  in  London, 

113  ;  constituents  of,  124. 
Gasholder,  the,  117. 
Glossopteris,  17. 
Graphite,  75. 
Green  Grease,  126. 

H. 

Hannay,  of  Glasgow,  79. 
Heavy  oils,  126. 
Humboldt's  safety-lamp,  90. 
Hydraulic  Main,  117. 

I. 

Impurities  in  coal-gas,  123. 

Indian  coals,  150. 

Insertion  of  rootlets  of  stigmaria^ 

31. 
Insufficiency     of      modern     forest 

growths,  10. 

Ireland  denuded  of  coal-beds,  54. 
Iron,  supplies  of,  105. 


Lepidodendra,  24. 
Lepidostrobi)  :  5. 
Lignite,  71. 

M. 

Marco  Polo,  134. 
Marsh  gas?  122. 
Medium  oils,  126. 

Metamorphism  of  coal  by  igneous 
agency,  74. 


Mountain  limestone,  44. 
Murdock's  use  of  gas,  113. 
Mussel  beds,  63. 

N. 

Naphthalin,  128. 
Neuropteris,  15. 
Newcastle,  charters  to,  103. 
Nitro-benzole,  157. 

O. 

Objections  to  use  of  coal,  103. 
Oils  from  coal  and  lignite,  12. 
Oil-wells  of  America,  131. 
Olefiant  gas,  123. 
Orthoceras,  62. 

P. 

Paraffins,  122. 

Peat,  68. 

Pecopteris^  17. 

Pennsylvanian  anthracite,  147. 

Persian  fire-worshipers,  133. 

Pitch,  126. 

Plumbago,  75. 

Polyzoa^  62. 

Prejudice  against  aniline  dyes,  162. 

Prohibitions  of  the  use  of  coal,  103. 

Proportions  of  explosive  mixtures, 

91. 

Psaromus,  17. 
Purifiers,  120. 
Pyrites  in  coal,  139. 

Q. 

Quantity  ^  of  coal    raised    in   Great 
Britain,  154. 

R. 

Reptiles  of  the  coal-era,  60. 
Resemblance  of  American  and  Brit- 
ish coal-^ra,  54. 
Retorts,  117. 
Roman  use  of  coal,  102. 
Rosanilines,  162. 
Royal  Commission  of  1866,  153. 

S. 

Sandstone,  how  formed,  38. 

Shales,  42. 

Sigillaria,  28. 

South  American  coals,  149. 


i08 


INDEX. 


Spores  of  lepidodendron,  26  ;  resin- 
ous matter  in,  28  ;  inflamma- 
bility of,  zoo. 

Steel-mill,  90. 

Sternbergia^  33. 

Stigmaria.)  30. 

Subsidence  throughout  coal-era,  55. 

Sulphur  in  coal,  106,  139. 

Sussex  iron- works,  105. 

T. 

Tar,  125. 

Testing  pits  by  the  candle,  89. 

Texas  coal,  148. 

Toluene,  discovery  of,  157. 

Torbanehill  mineral,  139. 

Trappers,  88. 

U. 


Underclays,  30,  44. 
Uses  to  which  coal  i: 


,s  put,  no. 


V. 


Vaseline,  131. 

Vegetation  of  the  coal  age,  9. 

Ventilation  of  coal-pits,  86. 


W. 

Washers,  119. 
Waste  of  fuel,  109. 
Wealden  lignite,  72. 
Westphalian  coal-field,  10. 


Y. 

Young's  Paraffin  Oil,  129. 

Z. 

Zoroastrians,  133. 


(6) 


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